poikilothermism

or poi·ki·lo·ther·my

[ poi-kuh-loh-thur-miz-uh m, poi-kil-uh- ]
/ ˌpɔɪ kə loʊˈθɜr mɪz əm, pɔɪˌkɪl ə- /

noun Zoology.

the state or quality of being cold-blooded, as fishes and reptiles.