Definition of cold-cock:
(v) :
(slang, transitive) To knock someone unconscious.
(v) :
(slang, transitive) To hit someone with a cold cock.
(v) :
(slang, transitive) To hit someone with a club, bottle, or any object that gives additional force to the blow.
(n) :
Alternative form of cold cock. [(slang) A small heavy object used to give additional force to a punch or other blow of the hand.]