Poikilothermous

Part of speech: adjective

Definitions

1. An organism characterized by a body temperature that is determined by external environmental factors rather than maintained at a constant level internally
2. A type of life form that does not regulate its internal temperature and instead adapts its warmth based on the surrounding climate
3. An entity whose thermal state is influenced by the ambient temperature rather than being self-regulated or homeostatically controlled

Etymology: "Poikilothermous" is built from two parts. The first, "poikilo-", comes from the Greek "poikilos", meaning "many-coloured", "dappled" or "variegated"; the same Greek root gives English words like "poikilitic" in mineralogy, where a crystal contains many small inclusions that give it a speckled look. The second part, "thermal", comes from the Greek "thermē", meaning "heat". Put together, the term describes a creature whose body temperature varies with its surroundings, a sense that the Greek ingredients only loosely suggest. The word is a scientific coinage from the modern period, assembled from classical elements by biologists rather than inherited from ancient usage. Its alternative form, "poikilothermal", is the more common spelling today, and the two are interchangeable in meaning. Their opposite, the warm-blooded animals that regulate their own heat, belong to a separate term that was formed on the same pattern.

Synonyms: cold-blooded

Antonyms: homeothermic, warm-blooded