An ectotherm is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

What ectothermic means?

ectotherm, any so-called cold-blooded animal—that is, any animal whose regulation of body temperature depends on external sources, such as sunlight or a heated rock surface. The ectotherms include the fishes, amphibians, reptiles, and invertebrates.

What does ectothermic mean for animals?

An ectothermic animal, also commonly known as a "cold-blooded" animal, is one who cannot regulate its own body temperature, so its body temperature fluctuates according to its surroundings. ... Rather, ectotherms rely on external or "outside" sources to regulate their body heat.