shoot from the hip - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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.