cold-blooded

/ˌkoʊld ˌˈblʌdəd/

/kəʊldˈblʌdɪd/

A cold-blooded animal has a body temperature that varies along with the outdoor temperature, and a cold-blooded person is someone who seems to feel no emotions. Your pet lizard may love you, but she's still cold-blooded.

During a hot, sunny day, a cold-blooded animal like a snake experiences a rise in body temperature, which it can only moderate by finding a shady spot to hide. When the sun goes down at night, a snake's body temperature falls. Cold-blooded people, on the other hand, regulate their body temperature even when it's chilly outside, like other warm-blooded animals. They're cruel and unfeeling, though. This meaning comes from the old-fashioned belief that blood temperature rises with emotion.

Definitions of cold-blooded

1. adjective

   having cold blood (in animals whose body temperature is not internally regulated)
   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
2. adjective

   without compunction or human feeling
   synonyms: cold, inhuman, insensate

   inhumane

   reflecting lack of pity or compassion