Green’s Dictionary of Slang

1. (US campus) a (punishment) beating.

1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Smackdown (noun) Beating someone up. Usually invoked as a disciplinary action.
2005		Mad mag. Mar. 53: [heading] Madison Avenue Smackdown!
2011		G. Hayward Corruption Officer [ebk] cap. 18: You know everybody heard about the smack down!

2. (US) violent speech, e.g. a dispute; an aggressive interrogation.

2008		R. Price Lush Life 161: ‘What’s going on?’ [...] ‘Some kind of family smackdown’ .
2023		M. Herron Secret Hours 17: There are advantages to being the one on foot in a motorbike–pedestrian smackdown.
2023		(con. 1962) J. Ellroy Enchanters 188: The Chief was pissed. Old man Zanuck beefed my smackdown.