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1. suck a butt
An insult that means precisely what the phrase implies, that the recipient should find a butt, and suck it.
The pronunciation is slower than one normally speaks, with emphasis on 'butt'.
Me: What up Dan?
Dan: Suck a BUTT.

Me: Nick Cannon so fly, he go school shopping and he buy three school.
Dan: Suck a BUTT.
2. suck a butt
Smoke a cigarette.
It's break time, let's go suck a butt!