cold-blooded

adjective4

1. •
   Having an unregulated body temperature; ectothermic.
2. •
   (figurative) Lacking emotion or compunction.

   • Here were assembled that great philosopher Mr. Subtile, the coldest-blooded metaphysician of the age. — 1797
3. •
   Of a type of horse: tall and muscular, usually good-natured and suitable for heavy work.
4. •
   Of an engine or vehicle: difficult to start; runs poorly until warmed up.