Definition of fin in English:



  • 1A flattened appendage on various parts of the body of many aquatic vertebrates, including fish and cetaceans, and some invertebrates, used for propelling, steering, and balancing.

    • ‘When hunting, they crawl on their outspread pectoral fins and sift through the sand.’
    • ‘When overcrowding occurred in the water, some of these fish, using their fins as rudimentary feet, took to the land and changed from gill breathing to lung breathing.’
    • ‘Then we saw the triangular fin of what appeared to be a shark.’
    • ‘You can see in the photos it's got a little tail fin.’
    • ‘Powerful fins propel the streamlined fish toward meals of smaller fish and squid - and away from hungry sharks.’
    • ‘It's a smooth skinned fish which can fold its small fins tight to the body, then, with its big sickle shaped tail, it can power itself through the water at some forty miles an hour.’
    • ‘Using its fins to balance, this fish is almost perfectly camouflaged against the background.’
    • ‘Hornsharks are named for the sharp spines located in front of their dorsal fins.’
    • ‘Once fully developed, they are released from the female and must attach to the gills or fins of a fish host within a few days or they will die.’
    • ‘A male frogfish courts a mature female by spreading all of his fins, jerking his body, and nibbling her as she swaggers across the ocean floor.’
    • ‘He then uses this to explain why there are no post-anal fins in fish: the tail is itself an appendage.’
    • ‘It has dark patches along its sides and back, but perhaps its most telling feature is the long spines that protrude from all over its body, excluding the fins and face.’
    • ‘Researchers say the fish shows how fins on freshwater species first began transforming into limbs some 380 million years ago.’
    • ‘Some fishes seek to compensate at low swimming speeds by extending their fins to increase area and hence the trimming force.’
    • ‘Not a true eel, it has long pelvic fins, which help it find food.’
    • ‘On the way back, I spotted a fin breaking the surface.’
    • ‘In essence, only the paired fins and the tail fin remain.’
    • ‘Finally, several authors have suggested that a fin closing against the body may result in thrust due to the acceleration of a jet of fluid behind the fish.’
    • ‘The ancient bone shares features with primitive fish fins, but also has characteristics of a true limb bone.’
    • ‘Could there ever be a situation where it would be to the advantage of a swimming vertebrate to have such fragile fins?’
    1. 1.1 An underwater swimmer's flipper.
      • ‘You realize that swimming without fins has become unbearable.’
      • ‘Now, the children are ready to try it on their own, using fins.’
      • ‘Using fins for drills and some kicking sometimes helps these swimmers.’
      • ‘I do a fair bit of technique work with fins and those sorts of things just to improve my stroke and I think it has come on a bit over the last year’
      • ‘We recommend that beginners and all children 8 and under use short fins to perform this stroke.’
      • ‘The next steps involve the whole stroke, removing the fins, underwater kicking to stroke start and finally the block start.’
      • ‘It's important, too, to allow for flexibility within a workout, be it with fins, paddles or buoys.’
      • ‘‘For sprint emphasis, we'll use short fins to simulate a more realistic natural kick,’ he says.’
      • ‘You take a look around the pool and are surprised to see that a number of swimmers are using fins, especially on kick sets.’
      • ‘Training equipment such as kickboards, pull buoys, and fins help all swimmers to isolate or emphasize certain movements.’
      • ‘To maximize your feel for this drill when first trying it, try wearing fins, which will also allow you to better maintain your balance while trying the drill.’
      • ‘But when you wear fins, your kick improves enough to make kicking worth the effort and you end up using use your legs more.’
      • ‘Finally, wear fins on some of your swimming sets.’
      • ‘All swimmers would like to have fins instead of feet.’
      • ‘They offer everything from diving equipment and lessons, to snorkeling gear and swim fins for an enjoyable underwater experience merely feet from your room.’
      • ‘A drill to develop this body position involves swimming with fins and a snorkel.’
      • ‘Do this exercise with and without fins, with and without a kick board, on your back, side, and stomach.’
      • ‘Allowing a swimmer to use a fin would send a message that his impairment is a disability and not just a characteristic of who he is as a person.’
      • ‘You'll just need a pair of training fins (also known as flippers) to wear on your feet.’
      • ‘We wear fins and masks, and we also wear pink caps so we can be visualized by one another and not lose anyone.’
    2. 1.2 A small flattened projecting surface or attachment on an aircraft, rocket, or car, for providing aerodynamic stability.
      • ‘Six spring-loaded fins are attached to the rear of the rocket motor.’
      • ‘When the pilot applied the brakes, the plane went forward on to its nose and turned upside down, causing serious damage to the aircraft nose and fin.’
      • ‘Attached to the end of the barrel are stationary fins that provide stability during flight.’
      • ‘A double-stepped bottom reduces the wetted surface area while above the water a fin at the rear stabilises the boat against cross-winds.’
      • ‘The fins and horizontal tail consoles are attached to tail beams.’
      • ‘There it is to undergo refurbishments, including repairs to a stabiliser fin damaged in transit.’
      • ‘The only obvious changes to the airframe are the new canopy and the taller fin extended back over the rudder.’
      • ‘He noticed that the gun fire had damaged what looked like a stabilization fin.’
      • ‘The ship has two shafts with controllable pitch propellers, two rudders and a pair of active stabilising fins.’
      • ‘Typically, moveable flaps on fins serve as airfoils.’
      • ‘The center fin was a fixed surface, extending vertically above the stabilizer at the center line of the airplane.’
      • ‘The control surfaces and the four fins open into position as the missile leaves the tube.’
      • ‘The vessel is fitted with two pairs of active stabilising fins and twin rudders and has bow and stern thrusters.’
      • ‘Aerodynamic fins located on the aft bay of the strap-ons also provided for flight control.’
      • ‘It was at that time that another depth charge exploded close to the aft starboard fin.’
      • ‘The centrifugal force of the roll causes the fins to unfold for aerodynamic stability in flight.’
      • ‘Two downward sweeping stabilizing fins sat near the engines, adding to the triangular appearance of the ship.’
      • ‘Next, he explored a different aesthetic with less prominent fins, visible rocket thrusters, and less visible similarity to marine life.’
      • ‘Years later when the definitive fin / rudder was retrofitted to this aircraft, these fairings remained unchanged.’
      • ‘Simply described, the fins improve directional stability by channeling and smoothing the airflow around the tailcone.’
    3. 1.3 A flattened projection on a device, used for increasing heat transfer.
      • ‘There are a total of six heat pipes running from the base to the aluminum fins.’
      • ‘This is another idea that in theory should help increase thermal conduction between the base and the fins, since they are all one piece.’
      • ‘They machined down the original fins of the power supply's heat sinks to create flat areas for attaching waterblocks.’
      • ‘The fins conduct heat from the tubes and then transfer it to the air flowing through the radiator.’
      • ‘On the building exterior, shading devices such as roof overhangs and fins or louvers above windows reduce glare.’
      • ‘In a normal heatsink, all the fins most be located close to the heat source (the CPU) to maximise dissipation.’
      • ‘The serrated fins actually increase the surface area to allow for more heat dissipation.’
      • ‘Its central element is the single-frame radiator grille, the outer chrome ring of which surrounds the painted grey fins of the grille with horizontal chrome strips.’
      • ‘The copper strip is folded into corrugated fins and cut with louvers, or turbulizers, to increase heat-dissipation capacity.’
      • ‘The top and bottom of the Cool Drive have fins for heat dissipation.’
      • ‘Actually, it's round and the idea behind it is that heat gets dissapated to the outer fins, where it gets cooled.’
      • ‘While the fins help dissipate the heat, you may be wondering where the fan is.’
      • ‘Concrete structural fins act as shading devices on the north-south axis.’
      • ‘Because of copper's heat retaining properties, thin fins are the way to go, coupled with an adequate fan.’
      • ‘It relies on radiation and passive convection from the heatsink fins that surround it, to dissipate heat.’
      • ‘As you can see, they pack the copper fins pretty tight, allowing for pretty good heat dissipation, rated for 938.89 BTU per hour.’
      • ‘Sandia's Mike Rightley said he has developed tiny liquid-filled pipes that shift heat to the edge of the computer where air fins or a tiny fan can disperse it into the air.’
      • ‘Framing the rear of the station are the blue internal heat radiator fins.’
      • ‘Looking closely at the fins you'll see that Hush's attention to detail is admirable, with each fin ridged for ultimate heat exchange.’
      • ‘It literally sandblasts the car every time it goes on track and gradually erodes all the surfaces and the cooling fins on the radiators.’


  • no object, with adverbial of direction Swim under water by means of flippers.

    ‘we finned along the side of the wreck’
    • ‘They then did some shallow water running followed by duck diving and finning (swimming with flippers).’
    • ‘So I finned and finned, periodically popping my head out of the water.’
    • ‘Do you find that you are finning all the time you are under water, unless resting on something.’
    • ‘I am motionless among all this life, just hovering, watching, occasionally finning forward to get a closer look.’
    • ‘It was finning slowly against the sandy bottom, down in the black heart of the river.’
    • ‘As we finned along the wreck, we were met by a large turtle munching contentedly on an outcrop of coral.’
    • ‘I hung, just waiting like everybody else, and amused myself watching dozens of divers finning quickly from one area to another, as the false alarms of sightings started to rack up.’
    • ‘Little protrudes in front of you, so the chest area is left clear for easy access to important equipment, and your legs don't bang and crash against the cylinders while finning.’
    • ‘The wreck lies on its port side, the only one of the light cruisers in this position, so we finned to the right along the now-vertical deck, taking in the sights.’
    • ‘A sand channel led us up and through to the other side, where we finned quickly towards the bow.’
    • ‘After my release from the tangle of ropes, we finned past broken windows along a companionway, and found a door ripped from its hinges.’
    • ‘It was a great dive if you could ignore the other divers, finning along a vertical wall that disappeared into the blue depths, and with fish and corals of virtually every shape and colour at the top of the reef.’
    • ‘We finned back along the port side and, after a bottom time of 15 minutes, our slow ascent up the shotline commenced.’
    • ‘One giant stride later, I was finning slowly towards the hull, watching as it disappeared into the sapphire gloom of 30m of water.’
    • ‘But so long as the whale shark made no discernible attempt to propel itself through the water I could, by finning vigorously, just about keep pace.’
    • ‘By now I had identified the ammo box as the problem and dragged my way, hand over hand, up the boulder floor of the underwater part of the lake chamber, all the time finning madly.’
    • ‘On one occasion we enjoyed a medium drift down a V-shaped channel, watching the usual teeming reef life flash by below and finning back every now and then to peer into crevices before being swept on.’
    • ‘We finned through the old barge, past fans of black coral, and circled the wheelhouse, joined by schools of barracuda.’
    • ‘We fell directly into the crater's mouth and finned over to the other side where, in deeper water, we caught a glimpse of several whitetip reef sharks.’
    • ‘I finned along the starboard side to the base of the bow, where I found a monster edible crab.’


Old English finn, fin, of Germanic origin; related to Dutch vin and probably ultimately to Latin pinna ‘feather, wing’.