cold-blooded

Synonyms

ectothermic, heterothermic, poikilothermic, poikilothermous

of animals except birds and mammals; having body temperature that varies with the environment

Antonyms:

warm-blooded

having warm blood (in animals whose body temperature is internally regulated)

homeothermic, homoiothermic, homothermic

of birds and mammals; having constant and relatively high body temperature

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Synonyms:

cold, inhuman, insensate

inhumane

lacking and reflecting lack of pity or compassion