Dictionary.com
definitions

poikilothermism

or poi·ki·lo·ther·my

[poi-kuh-loh-thur-miz-uh m, poi-kil-uh-]
noun Zoology.
  1. the state or quality of being cold-blooded, as fishes and reptiles.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018