1
general::
Speak or act recklessly or impulsively, as in Steve isn't very tactful; indeed, he's known for shooting from the hip. This expression transfers the fast shooting accomplished by drawing a gun from a holster and shooting without raising it to quick speaking or acting. [Slang; mid-1900s] For a similar transfer, see SHOOT OFF ONE'S MOUTH.
American Heritage Idioms
2
general::
Phrase(s): shoot from the hip
1. Lit. to fire a gun that is held at one’s side, beside one’s hip. (This increases one’s speed in firing a gun but is much less accurate.) • When I lived at home on the farm, my father taught me to shoot from the hip. • I quickly shot the snake before it bit my horse. I’m glad I learned to shoot from the hip. 2. Fig. to speak directly and frankly. (Alluding to the rapidness of firing a gun from the hip.) • John has a tendency to shoot from the hip, but he generally speaks the truth. • Don’t pay any attention to John. He means no harm. It’s just his nature to shoot from the hip.
McGrawhill's American Idioms And Phrasal Verbs