n.
   - the quality of being hot; high temperature. 
▸Physics  heat seen as a form of energy arising from the random motion of the molecules of bodies.
 ▸technical the amount of heat needed for or evolved in a specific process.
 ▸a source or level of heat for cooking.
 - intensity of feeling, especially of anger or excitement. 
▸
(the heat)
 informal intensive and unwelcome pressure.
 - a preliminary round in a race or contest.
 
v.
  - make or become hot or warm.
 - 
(heat up)
 become more intense and exciting. 
▸
[
as adj. heated]
 inflamed with passion or conviction:
 a heated argument.
  ▸archaic inflame; excite.
 
 
  Phrase
  
    - in the heat of the moment
 while temporarily angry or excited and without stopping to think.  - on 
(or N. Amer. in)
 heat
 (of a female mammal) in the receptive period of the sexual cycle; in oestrus. 
   
  Derivative
  
  Etymology
  OE hætu (n.), hætan (v.), of Gmc origin; rel. to hot.