Exothermic

Exothermic has several meanings, including:

• In biology, an exothermic or poikilothermic animal is one that requires external sources of heat (usually sunlight) to maintain its internal temperature: for example, reptiles. See also endothermic.
• In chemistry, an exothermic reaction is one that produces heat: for example, combustion. See also thermodynamics, chemical thermodynamics.