the.com/poikilotherm

means An organism, like a reptile or fish, whose internal body temperature shifts along with its surroundings rather than being internally regulated.

from Built from Greek parts: 'poikilos' meaning varied, dappled, or mottled, and 'therme' meaning heat — so literally 'varied-heat.' Scientists coined it in the 19th century as a more precise alternative to the folk label 'cold-blooded,' which is misleading since a lizard basking in the sun can have warmer blood than a mammal. 'Poikilos' shows up elsewhere in biology too, as in 'poikiloderma' for mottled skin — the root always pointing at variation and patchiness rather than any fixed state.