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1.
1. A shorter verson of definitely.

2. One who can't hear shit.

3. A definition on urbandictionary.com.
1. "hey, dude, you should deff come over"

2. "i can't hear shit i'm so deff"

3. "go look at the deff for deff on UD"
by joeybnukkas April 14, 2007
 
2.
abbreviation for the word 'definitely'
'Are you going to come out to the movies with us tonight'

'Yeah deffs, i would love to!'
by Millie...ew November 06, 2008
 
3.
A shorter version of definitely .
Jessica: (Takes pencil)
Teacher: Class, pick up your pencils and begin your test.
Kathy: Oh, but i was deff using that pencil tho!

:-) , coming from a person who uses the word ALOT !
by Breezyyyy March 16, 2010
 
4.
a form of wreaking HAVOK in class or to destroy EVERYTHING IN CLASS. derived from DEATH, only too awesome to be called death. DEFF is often heard being screamed in a deep voice DEFFFFFFFFFFFFFFFFFFFFFFFF in class when it is in a defffffff con 1 status(lol).
(Theres 8 people fighting and 5 people screaming while throwing shit everywhere, the teacher has passed out)
Me: DEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
by Tiko310 January 28, 2009
 
5.
Deff- originating in georgia, meaning Designated Extremely Fat Friend. Used primarily when u and your buddies see a hot chick with a fat friend.
guy one "damn you see that girl"
guy two" which one"
guy one "the one thats behind the Deff"
guy two"ok got ya yah shes straight"
by Chris Nix August 26, 2008
 
6.
shortend version of "deffinitly". mainly used by asshats who don't like to spell out words on aim.
joe: you should deff come over
bob: fuck you.
by asshat CJ March 18, 2007
 
7.
A rap group with brutal lyrics, and no production.

Current members:
Deff Nigger- vocals
Bleyend Chink- Beats/backup vocals
www.myspace.com/deffnigga
by Bleyend January 08, 2009