thermal

/ˈθʌrməl/

/ˈθʌməl/

Other forms: thermals

If it has to do with heat, it’s thermal. Wearing a thermal shirt under your sweater helps you stay warm on a brutally cold day. Your thermal coffee mug keeps your coffee hot.

The Greek word therme, meaning “heat,” is the origin of the adjective thermal. Something that is thermal is hot, retains heat, or has a warming effect. If your sweatshirt has a thermal lining, its texture might remind you of a waffle-that's what traps your body heat. Also, there are large currents of warm air that flow upwards — these are what gliders or big birds like hawks ride to stay afloat — one type of those currents is called a “thermal.”

Definitions of thermal

1. adjective

   relating to or associated with heat
   “thermal movements of molecules”

   “thermal capacity”

   synonyms: caloric, thermic

   antonyms:

   nonthermal

   not involving heat
2. adjective

   caused by or designed to retain heat
   “a thermal burn”

   “thermal underwear”

   synonyms:

   hot

   used of physical heat; having a high or higher than desirable temperature or giving off heat or feeling or causing a sensation of heat or burning
3. adjective

   of or relating to a hot spring
   “thermal water”
4. noun

   rising current of warm air
   type of:

   air current, current, current of air, wind

   air moving (sometimes with considerable force) from an area of high pressure to an area of low pressure