The term 'USE A STUN GUN ON' can be summarized by two crossword solutions: ZAP (3 letters) and TASE (4 letters). ZAP is a slang term for shocking or stunning someone with an electric current, while TASE is an acronym for 'Thomas A. Swift's Electric Rifle', a type of stun gun. Both terms refer to the use of a stun gun on someone, which is a non-lethal weapon that temporarily incapacitates a person by delivering an electric shock.