Definition of thermal in English:



  • 1Relating to heat.

    • ‘Heat, or thermal energy, is transferred from one body to another by virtue of a temperature differential.’
    • ‘Other considerations include heat conductivity and thermal expansion.’
    • ‘When measuring heating effects, a unit of thermal energy known as a calorie is used.’
    • ‘Either way, the gauze, acting as a heat sink, removes the thermal energy from the system so that the temperature above or below it is not sufficient to ignite the gas.’
    • ‘Atoms may acquire energy that excites electrons by random thermal collisions, collisions with subatomic particles, or by absorbing a photon.’
    • ‘In other words, water vapor has a low heat capacity and poor thermal conduction.’
    • ‘At low ambient temperatures, most bird species increase heat production to achieve thermal balance.’
    • ‘Well, as we already know, aluminum is a popular material used for heatsinks due to its thermal properties.’
    • ‘For example, the mesh could filter the thermal radiation from a heat source so that only the optimal wavelengths reach the device.’
    • ‘As the world braces itself for a possible terrorist nuclear attack, several projections and scenarios as to possible deaths from shock waves and thermal and ionising radiation injury have been made.’
    • ‘In thermal recovery, heat is the most important agent.’
    • ‘Basic research into the electrical and thermal properties of metallic, magnetic and organic materials is leading to the discovery of novel superconductors.’
    • ‘Microjets can be powered by compressed air, thermal bubbles, and even acoustic waves.’
    • ‘An individual should rely on the use of water alone to prevent heat injury or thermal stress.’
    • ‘The thermal properties of copper are such that it can draw heat away very quickly indeed, but it also has a tendency to keep that heat.’
    • ‘Approximately 35% of the energy from a nuclear explosion is an intense burst of thermal radiation, ie heat.’
    • ‘PCBs were the miracle fluids, used widely in the western world in transformers, turbines, and vacuum pumps for their high thermal stability and dielectric properties.’
    • ‘The polystyrene-based material contains microscopic flakes of graphite that reflect heat, making it difficult for thermal radiation to penetrate.’
    • ‘If you have a high density of atoms and you put thermal energy into the system you will raise the temperature.’
    • ‘Nuclear weapons produce their energy in three distinct forms: blast; heat or thermal radiation; and nuclear radiation.’
    1. 1.1
      another term for geothermal
      • ‘Similarly, the other regions of India which are nearer to thermal power stations should also start this technique.’
      • ‘Such use has not only reduced costs but has also helped thermal power stations and paper mills dispose of fly-ash, a pollutant.’
      • ‘Work is continuing on the refurbishment of two units at a large thermal power station in Baghdad.’
      • ‘For a thermal power station the capital costs are apparently very similar, and the thermal power station would release more carbon dioxide into the atmosphere.’
      • ‘A wind farm, for example, is likely to occupy more land than a thermal power station.’
      • ‘Around 120 megawatts of new wind capacity has been announced in the last couple of weeks, and two thermal power stations are just waiting for the gas to allow them to be built.’
      • ‘Leaving his job as a designer of thermal power stations, he took a plunge into politics.’
      • ‘Work is also continuing on the refurbishment of two units at a large thermal power station in south Baghdad.’
      • ‘However, it takes three to five years to build a thermal power station.’
      • ‘So, if you're thinking about a relaxing, romantic weekend, then Bath could quite possibly be your dream city, with fantastic luxury hotels, small romantic restaurants, and don't forget to unwind in Britain's only natural thermal spa.’
      • ‘It is designed for corporate firms involved in manufacturing processes like petrochemical industries and thermal power stations that require large quantities of water.’
      • ‘She is the daughter of Aramkumar, an engineer at the thermal power station in Tuticorin, and Annam, who is an engineer at the Tamil Nadu Water and Drainage Board.’
    2. 1.2(of a garment) made of a fabric that provides exceptional insulation to keep the body warm.
      ‘thermal underwear’
      • ‘Fortunately, I'd packed my thermal underwear, as it was actually freezing cold.’
      • ‘A former Miss UK who traded her swimsuit for thermal underwear and fleecy jackets to compete in the world's toughest endurance challenge is keeping pace with the leaders after a slow start.’
      • ‘Next I rode around on a double-decker bus for about an hour, got something to eat and went shopping at Harrods for thermal underwear.’
      • ‘Despite layers of thermal underwear and polar fleeces under my oilskins, I am so cold that I have lost all feeling in my right hand.’
      • ‘He too was dressed in his pajamas, a green thermal shirt and green striped pants, along with old, worn-out brown shoes and his jacket.’
      • ‘No wonder I needed thermal underwear on Monday.’
      • ‘Just pray they don't spot the thermal underwear.’
      • ‘I've resorted to thermal underwear, several layers of jerseys, winter stockings and a polar fleece jacket.’
      • ‘Whatever the weather, grandmother Doreen Stansfield can be seen out in Haworth in her yellow coat, thermal gloves and peaked cap.’
      • ‘Cold weather gloves, jackets and insulated flying boots combined with thermal underwear will keep you warm during a flight and can save your life in an emergency.’
      • ‘Charles soon joined the table, smoothing out his hair and pulling a lacrosse jersey over his thermal shirt.’
      • ‘It has not been much warmer in France than it was in Belgium and we started the first stage in leg warmers, thermal vests, gloves and hats.’
      • ‘No, I wore thermal nightwear on winter nights only.’
      • ‘This Christmas my parents gave me thermal underwear.’
      • ‘But the sun has barely set on this all-night shoot and I'm already wishing I'd brought thermal underwear and a foil blanket.’
      • ‘Which means girls like me, who like to wear a nice pair of heeled boots and a short skirt, are instead having to wear thermal underwear, thick trousers and snow boots.’
      • ‘Bed socks, nightcaps, thermal underwear and warm nightclothes are a good idea.’
      • ‘I wear lots of thermal underwear under the suit, which helps.’
      • ‘Clad in thermal underwear, a drysuit, flippers and gloves, and wearing weights on her legs and belt, she set off at midnight.’
      • ‘If you really want to know, we ate at a food court and shopped for thermal underwear.’
      thick, chunky, thermal, winter, woolly
      View synonyms


  • 1An upward current of warm air, used by gliders, balloons, and birds to gain height.

    • ‘Overhead, hawks circle in a rising thermal against a Carolina blue sky.’
    • ‘North wind and strong thermals allowed a very high average speed, especially between the first and the second turn point.’
    • ‘There are illustrative charts that explain phenomena like birds soaring using thermals.’
    • ‘Through the enveloping silence came the sound of the wind singing through the passes; the tinkle of meltwater running off the ice and the occasional cry of a bird hanging in the thermals overhead.’
    • ‘I find a little lift before I get to him then join him in a good thermal as he gets over the ridge line 7 kilometers from the turn point.’
    • ‘This rising air is part of a thermal, a rising current of air which develops over parts of the surface that are warmer than their surroundings.’
    • ‘High in the sky frigate birds circle in the thermals, black wings spread wide, waiting and watching.’
    • ‘Pilots typically seek out thermals or currents created by ridges to extend their flights.’
    • ‘You don't need thermals over a warm landmass to create a sea breeze.’
    • ‘It indicates what rate of climb you seem to be expecting in the next thermal based on your current air speed.’
    • ‘The lift wasn't strong at all, but we were moving quickly from thermal to thermal.’
    • ‘Out of the corner of my eye, I watched a bird streak past, riding a thermal up over the building.’
    • ‘Around noon I saw several hundred rooks circling upward in a thermal.’
    • ‘By using thermals, gliders can stay aloft for hours without using power.’
    • ‘High in the air probably 1000 feet up I saw a small group of rooks riding a thermal just like they were a kettle of broad-wing hawks.’
    • ‘I hit a strong thermal in the middle and with my arms stretched at the bar I was going vertically up.’
    • ‘The air above these places is heated and eventually starts to rise forming a thermal which we can use to gain height.’
    • ‘The thermals are strong enough to overcome the north winds and it is easy to climb up on the lee sides of the peaks and ridges.’
    • ‘However, if the upper winds are strong, you know that thermals will bring that wind down earlier and it will be stronger and gustier.’
    • ‘Before too much height is lost, the pilot will seek another thermal, gain height in it, and then set off on course yet again.’
    • ‘All of them were looking up into the sky at two birds, soaring on thermals.’
  • 2A thermal garment, especially underwear.

    • ‘I have my thermals and one of the said wacky hats out ready.’
    • ‘I had no thermals, but cut a dash with pyjama bottoms under my jeans and a borrowed Cossack hat.’
    • ‘For sailing I would advise packing at least the same amount of clothes, thermals, jerseys and long johns again.’
    • ‘I was bundled up in only one coat and a long-sleeved tee shirt, with some thermals and pants over them, along with hiking boots.’
    • ‘Even wrapped up with an extra set of thermals under a drysuit and thick winter gloves, the water is bitterly cold.’
    • ‘She has put away her thermals, waterproofs and woolly hat to don a smart black suit, white shirt, black cravat, dark tights and low-heeled shoes as the Mayor's Attendant.’
    • ‘Before meeting her, I might have listed winter survival equipment as follows: thermals, a woolly hat and a flask of whisky.’
    • ‘Specialist clothing and footwear is provided, but you do need to come equipped with a good set of thermals, hat, socks and gloves.’
    • ‘It works for pottering around in barefoot at home or layered up with thermals, tights and a cardie for winter workdays.’
    • ‘How about trekking to one of the planet's coldest spots wrapped up in thermals and Gore-Tex, all in the quest for artistic inspiration?’
    • ‘Leave the thermals at home, forget the woolly hat and the three pairs of socks, and instead, don stylish sunglasses and a shirt.’
    • ‘I went equipped not only with two pairs of gloves, two jumpers, two pairs of trousers, thermals, fleece, woolly hat and ski jacket, but my iPod and the thickest book I could find.’
    • ‘Even with my thick bike gear and thermals on, I was so cold I nearly turned back - and this was at midday.’


Mid 18th century (in the sense relating to hot springs): from French, from Greek thermē heat.