Definition of thermal in English:



  • 1Relating to heat.

    ‘thermal conductivity’
    ‘the thermal properties of food’
    • ‘At low ambient temperatures, most bird species increase heat production to achieve thermal balance.’
    • ‘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.’
    • ‘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 thermal recovery, heat is the most important agent.’
    • ‘The polystyrene-based material contains microscopic flakes of graphite that reflect heat, making it difficult for thermal radiation to penetrate.’
    • ‘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.’
    • ‘Basic research into the electrical and thermal properties of metallic, magnetic and organic materials is leading to the discovery of novel superconductors.’
    • ‘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.’
    • ‘Nuclear weapons produce their energy in three distinct forms: blast; heat or thermal radiation; and nuclear radiation.’
    • ‘Heat, or thermal energy, is transferred from one body to another by virtue of a temperature differential.’
    • ‘Well, as we already know, aluminum is a popular material used for heatsinks due to its thermal properties.’
    • ‘In other words, water vapor has a low heat capacity and poor thermal conduction.’
    • ‘Other considerations include heat conductivity and thermal expansion.’
    • ‘Approximately 35% of the energy from a nuclear explosion is an intense burst of thermal radiation, ie heat.’
    • ‘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.’
    • ‘If you have a high density of atoms and you put thermal energy into the system you will raise the temperature.’
    • ‘When measuring heating effects, a unit of thermal energy known as a calorie is used.’
    1. 1.1
      ‘thermal power stations’
      another term for geothermal
      • ‘Such use has not only reduced costs but has also helped thermal power stations and paper mills dispose of fly-ash, a pollutant.’
      • ‘However, it takes three to five years to build a thermal power station.’
      • ‘Leaving his job as a designer of thermal power stations, he took a plunge into politics.’
      • ‘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.’
      • ‘Similarly, the other regions of India which are nearer to thermal power stations should also start this technique.’
      • ‘Work is continuing on the refurbishment of two units at a large thermal power station in Baghdad.’
      • ‘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.’
      • ‘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.’
      • ‘It is designed for corporate firms involved in manufacturing processes like petrochemical industries and thermal power stations that require large quantities of water.’
      • ‘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.’
      • ‘Work is also continuing on the refurbishment of two units at a large thermal power station in south Baghdad.’
      • ‘A wind farm, for example, is likely to occupy more land than a thermal power station.’
    2. 1.2(of a garment) made of a fabric that provides exceptional insulation to keep the body warm.
      ‘thermal underwear’
      • ‘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.’
      • ‘I wear lots of thermal underwear under the suit, which helps.’
      • ‘Just pray they don't spot the thermal underwear.’
      • ‘No wonder I needed thermal underwear on Monday.’
      • ‘No, I wore thermal nightwear on winter nights only.’
      • ‘Fortunately, I'd packed my thermal underwear, as it was actually freezing cold.’
      • ‘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.’
      • ‘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.’
      • ‘I've resorted to thermal underwear, several layers of jerseys, winter stockings and a polar fleece jacket.’
      • ‘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.’
      • ‘This Christmas my parents gave me thermal underwear.’
      • ‘Charles soon joined the table, smoothing out his hair and pulling a lacrosse jersey over his thermal shirt.’
      • ‘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.’
      • ‘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.’
      • ‘Whatever the weather, grandmother Doreen Stansfield can be seen out in Haworth in her yellow coat, thermal gloves and peaked cap.’
      • ‘Clad in thermal underwear, a drysuit, flippers and gloves, and wearing weights on her legs and belt, she set off at midnight.’
      • ‘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.’
      • ‘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.’
      • ‘If you really want to know, we ate at a food court and shopped for thermal underwear.’


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

    • ‘You don't need thermals over a warm landmass to create a sea breeze.’
    • ‘Out of the corner of my eye, I watched a bird streak past, riding a thermal up over the building.’
    • ‘North wind and strong thermals allowed a very high average speed, especially between the first and the second turn point.’
    • ‘Pilots typically seek out thermals or currents created by ridges to extend their flights.’
    • ‘Around noon I saw several hundred rooks circling upward in a thermal.’
    • ‘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.’
    • ‘The lift wasn't strong at all, but we were moving quickly from thermal to thermal.’
    • ‘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.’
    • ‘High in the sky frigate birds circle in the thermals, black wings spread wide, waiting and watching.’
    • ‘It indicates what rate of climb you seem to be expecting in the next thermal based on your current air speed.’
    • ‘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.’
    • ‘However, if the upper winds are strong, you know that thermals will bring that wind down earlier and it will be stronger and gustier.’
    • ‘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.’
    • ‘Before too much height is lost, the pilot will seek another thermal, gain height in it, and then set off on course yet again.’
    • ‘By using thermals, gliders can stay aloft for hours without using power.’
    • ‘There are illustrative charts that explain phenomena like birds soaring using thermals.’
    • ‘All of them were looking up into the sky at two birds, soaring on thermals.’
    • ‘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.’
    • ‘Overhead, hawks circle in a rising thermal against a Carolina blue sky.’
    • ‘I hit a strong thermal in the middle and with my arms stretched at the bar I was going vertically up.’
  • 2A thermal garment, especially underwear.

    • ‘Specialist clothing and footwear is provided, but you do need to come equipped with a good set of thermals, hat, socks and gloves.’
    • ‘Before meeting her, I might have listed winter survival equipment as follows: thermals, a woolly hat and a flask of whisky.’
    • ‘For sailing I would advise packing at least the same amount of clothes, thermals, jerseys and long johns again.’
    • ‘I had no thermals, but cut a dash with pyjama bottoms under my jeans and a borrowed Cossack hat.’
    • ‘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.’
    • ‘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?’
    • ‘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 with my thick bike gear and thermals on, I was so cold I nearly turned back - and this was at midday.’
    • ‘It works for pottering around in barefoot at home or layered up with thermals, tights and a cardie for winter workdays.’
    • ‘I have my thermals and one of the said wacky hats out ready.’
    • ‘Leave the thermals at home, forget the woolly hat and the three pairs of socks, and instead, don stylish sunglasses and a shirt.’
    • ‘Even wrapped up with an extra set of thermals under a drysuit and thick winter gloves, the water is bitterly cold.’
    • ‘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.’


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