The Collaborative International Dictionary
To go off halfcocked
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. To go off half-cocked, To go off halfcocked.
To be discharged prematurely, or with the trigger at half cock; -- said of a firearm.
To do or say something without due thought or care.