'To go off halfcocked' definitions:

Definition of 'To go off halfcocked'

From: GCIDE

Halfcock \Half"cock`\ (-k[o^]k`), v. t. [imp. & p. p. Halfcocked(-k[o^]kt); p. pr. & vb. n. Halfcocking.] To set the cock of (a firearm) at the first notch. [1913 Webster]
To go off half-cocked, 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] [1913 Webster]