1) The sound a thumper makes when it busts off

2) A common adlib used by certain rappers from North Oakland (Lil Rue, HD, etc..)
"Every day it's like I got some new niggas to kill (SMACK SMACK)" - HD on Minister Of Defense / Extortion Muzik 2
by yay area representative March 31, 2011
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The more updates name for "sandles" or " flip-flop".
Derrived from the sound the "shoe" makes when hitting your foot.
by Cher-in-Surrey November 02, 2010
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First invented (allegedly) by Dan Mace. Means let's get things done. A whole episode of 368 by Casey Neistat is titled after this phrase "SMACK IT."
For example, let's just smack it on the plane, meaning let's get it done when on the plane.
by Amycrackpot April 20, 2018
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Heroin. Most frequently used in the 60s.
When the smack begins to flow, I really don't care anymore...
by Lurhstaap December 28, 2003
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To have sex from the back, hit it from behind, doggystyle. Doing this hard and fast so that it makes a smacking noise.
That girls hot, I want to smack that.
by jennw January 12, 2007
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Smack On means to propose a fight with someone. Generally in a joking manner but can definitely can be used very effectively in a real situation. Smack On is closely associated with the term "punch on".
Joking:
Luke: "You suck apples"
Brad: "Smack on cunt"

Serious:
Josh: "I fucked your ex on a trampoline!"
Ryan: "Smack on cunt!"
by KinnyMcbinspin February 04, 2014
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