poi·kil·o·therm  (poi-kĭl'ə-thûrm')  n. An organism, such as a fish or reptile, having a body temperature that varies with the temperature of its surroundings; an ectotherm. [Greek poikilos, spotted, various; see peig- in Indo-European roots + -therm.] poi'ki·lo·ther'mi·a (-thûr'mē-ə) n., poi'ki·lo·ther'mic (-mĭk) adj. |