exothermic
Pronunciation: /ˌɛksə(ʊ)ˈθəːmɪk/
adjective
Chemistry- (of a reaction or process) accompanied by the release of heat. The opposite of endothermic (sense 1)
- (of a compound) formed from its constituent elements with a net release of heat.

Origin:
late 19th century: from French exothermique