four-twenty, v. — Green’s Dictionary of Slang

four-twenty v.

also 4:20

(US black/drugs) to smoke marijuana.

1997–2000		Da Bomb 🌐 1: 420: To smoke marijuana. Hey man, what time is it? 420.
2000		Ebonics Primer at www.dolemite.com 🌐 four-twenty (4:20) Definition: time to smoke Example: Shit nigga, lets go 4:20!