exothermic

adj

1. That releases energy in the form of heat.

   “These can be differentiated on a thermal scan where an endothermic transition indicates enantiotropes and an exothermic transition indicates monotropes.”

2. That releases heat during its formation, and absorbs it during its decomposition.
3. Of an animal: whose body temperature is regulated by external factors; cold-blooded.

noun

1. A substance that releases heat energy.