Halfcock \Half"cock`\, v. t. [imp. & p. p. {Halfcocked}; p. pr. & vb. n. {Halfcocking}.] To set the cock of (a firearm) at the first notch. {To go off halfcocked}. (a) To be discharged prematurely, or with the trigger at half cock; -- said of a firearm. (b) To do or say something without due thought or care. [Colloq. or Low]