[per.cus.sion] n [ME, fr. L percussion-, percussio, fr. percutere to beat, fr. per- thoroughly + quatere to shake] (15c) 1: the act of percussing: as a: the striking of a percussion cap so as to set off the charge in a firearm b: the beating or striking of a musical instrument c: the act or technique of tapping the surface of a body part to learn the condition of the parts beneath by the resultant sound
2: the striking of sound on the ear
3: percussion instruments that form a section of a band or orchestra -- percussion adj