This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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• Wordscraper
• Wordosaur

adj. Capable of maintaining a relatively constant body temperature independent of the surrounding environment.

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

"Moreover, they are truly homeothermic, requiring maintenance of a constant internal body temperature that is considerably above environmental temperature."

warm-blooded   

cold-blooded    ectothermic   

warm-blooded    homothermic