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1.
To smoke up is to let another person smoke marijuana with you without payment.
Guy 1: You got bills?
Guy 2: Nah man, I'm dead broke.
Guy 1: It's aight, I'll smoke you up on this blunt.
by Dan March 24, 2005
 
2.
verb. (trans.) to share cannabis with one or more people
"Hey, we smoke brad up all the time but he never buys-it's bullshit!"
by Ganja Man February 14, 2005
 
3.
To 'smoke up', is to have a hit of cannibus sativa from a bong or waterpipe.
"Do you want to have a 'session' next Saturday?"
"Yo' bruz, I 'smoke up' everyday, its jus' a matter of if yo' wanna be there or not!"
by Diego August 31, 2003
 
4.
To tell someone to 'smoke up' is asking them to hurry up with the joint when they're taking fucking ages with their tokes.
Guy 1: "Is this your 3rd toke?"
Guy 2: "Nah, 2nd."
Guy 1: "Smoke the fuck up, then!"
by Rep August 24, 2004