v. 1. To discharge (a gun); explode; fire. Willie accidentally let off his father's shotgun and made a hole in the wall.
Synonym: GO OFF, LET LOOSE 2 . 2. To permit to go or escape; excuse from a penalty, a duty, or a promise. Two boys were caught smoking in school but the principal let them off with a warning. Mary's mother said that she would let Mary off from drying the supper dishes. The factory closed for a month in the summer and let the workers off.
Compare: LET GO. 3. or informal