poikilotherm
noun
poi·ki·lo·therm pȯi-ˈkē-lə-ˌthərm 
-ˈki-
-ˈki- : an organism (such as a frog) with a variable body temperature that tends to fluctuate with and is similar to or slightly higher than the temperature of its environment : a cold-blooded organism
poikilothermic
ˌpȯi-kə-lō-ˈthər-mik
adjective 
Did you know?
Poikilotherms are also called "ectotherms" or "cold-blooded animals." Such creatures are the thermoregulatory opposites of "endotherms" or "homeotherms" - better known to most of us as "warm-blooded animals" - which are able to maintain a fairly high and constant body temperature relatively independent of the temperature of the surroundings. "Stenotherms" are creatures that can survive only within a very narrow temperature range. The "-therm" in all of these terms comes from the Greek thermē, which means "heat."
Word History
Etymology
Greek poikilos variegated + International Scientific Vocabulary -therm — more at paint
First Known Use
1920, in the meaning defined above
Medical Definition
poikilotherm
noun
poi·ki·lo·therm ˈpȯi-ki-lə-ˌthərm (ˌ)pȯi-ˈkil-ə-
(ˌ)pȯi-ˈkil-ə- : an organism (as a frog) with a variable body temperature that is usually slightly higher than the temperature of its environment : a cold-blooded organism
called also heterotherm