Mos-Def 

As coined by the legendary rapper himself, "Mos-Def" refers to a thing, person, experience etc which is "mos" (or most, hugely, a lot), "def" (excellent, awesome; NOT short for 'definitely').

Mos-Def's changing his rap name to "Yasiin"?? Don't sweat it, he's still the MOS DEF rapper out.... after Chuck D of course..

Mos-Def by LittleRedFox.com.au September 28, 2011

Mos-Def 

Short for most Definatly

I mos-def love fries from McDondals

Mos-Def by And the Pickles January 1, 2007

mos def 

a fly MC, often apperaring alongside Talib Kweli, The Roots, or Common

mos def is one ill nigga, son

mos def by Ponyboy August 3, 2003

mos def 

Slang for 'most definitely'

"Wan' a cig, man? "Mos' def!"

mos def by David Allison August 21, 2003

mos def 

A man who can not only act with 5 star ability, but can also create some of the best shit out on recording ever.

Mos Def yet an actor of decent fame still keeps his hip-hop true.

mos def by Paul October 2, 2003

mos def 

(adv.) meaning: most definitely; the phrase also pays homage to the infamous emcee, Mos Def.

"You better hit me up with those tracks."
"I'll mos def hit you back, hommie."

mos def by kduballstar October 6, 2005

mos def 

1.: A slang term for "most definitely."
2.: A rapper.
3.: Deaf - this useage is the least common, mostly by people who didn't understand it in the first place or mispronounced.

1.: "Am I going to the party? Mos def!"
2.: "Mos Def is one of the best rappers of our time."
3.: "After that concert, they're mos def."

mos def by Gillian January 4, 2005