1) short for 'most definately'
2) Hell yea; fo'sho'
3) the pun is on the rapper Mos Def, however his name is completely irrelevant to this insert
*an asian girl walks by with a big ass*
1)Would you hit that?
2)Most Def!!!
by bringas June 30, 2005
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(coming from "most definently")...meaning you strongly agree with someone else offer
Yo id rip that girl wide open...

Oh most def...most def
by bt June 21, 2005
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Due 1: "Dude, we should get more beer."

Dude 2: "Most Def."
by Beavis McButthead June 11, 2010
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