coldblooded

Adjective

cold-blooded (comparative more cold-blooded or colder-blooded, superlative most cold-blooded or coldest-blooded)

1. Having an unregulated body temperature; ectothermic.
   • “Dead animals radiate heat,” he said. “When you take one down, you can feel it pouring from the wounds. But not this thing.” / “What does that mean?” she asked. / “Cold-blooded maybe, or colder-blooded than we’re used to.” / “Might explain why the heat sensors have trouble picking them up,”...2010, Graham Brown, chapter 35, in Black Rain: A Thriller, New York, N.Y.: Dell, →ISBN, page 344

   Antonyms:

   warm-blooded

2. (figuratively) Lacking emotion or compunction.
   • Here were aſſembled that great philoſopher Mr. Subtile, the coldeſt-blooded metaphyſician of the age.1797, [Isaac D’Israeli], “A Philosophical Party. The Character of a great Philosopher.”, in Vaurien: or, Sketches of the Times: Exhibiting Views of the Philosophies, Religions, Politics, Literature...

   Synonyms:

   emotionless, reptilian, reptitious, sangfroid, alexithymic, apathistical, clinical, dull, phlegmatic, cold-hearted

   Antonyms:

   warm-blooded

3. Of a type of horse: tall and muscular, usually good-natured and suitable for heavy work.

   Antonyms:

   warm-blooded

4. Of an engine or vehicle: difficult to start; runs poorly until warmed up.