The Collaborative International Dictionary of English v.0.48:

Cold-blooded \Cold"-blood`ed\, a.
   1. Having cold blood; -- said of fish or animals whose blood
      is but little warmer than the water or air about them.
      [1913 Webster]

   2. Deficient in sensibility or feeling; hard-hearted.
      [1913 Webster]

   3. Not thoroughbred; -- said of animals, as horses, which are
      derived from the common stock of a country.
      [1913 Webster]

WordNet (r) 3.0 (2006):

cold-blooded
    adj 1: without compunction or human feeling; "in cold blood";
           "cold-blooded killing"; "insensate destruction" [syn:
           cold, cold-blooded, inhuman, insensate]
    2: having cold blood (in animals whose body temperature is not
       internally regulated) [ant: warm-blooded]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "cold-blooded":
   apathetic, barbaric, barbarous, brutal, callous, cool, cruel,
   dispassionate, heartless, imperturbable, indifferent, inhuman,
   insensitive, merciless, pitiless, poikilothermic, ruthless, savage,
   steely, stony, thick-skinned, uncaring, unemotional, unexcited,
   unfeeling, unimpassioned, unmoved, unresponsive, unsympathetic,
   vicious