Top Definition
at 4:20 (PM or AM) one must smoke any marijuana substance available. (this includes, but is not limited to, eating, snorting, fucking, cooking, etc.)
Girl: hey what time is it?

Guy: its 4:20 PM

Girl: i think im gonna go outside and smoke a cigarette.

Guy: Rule 420 bitch!
by GANJAGANJ December 18, 2008
4 Words related to Rule 420

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