Extremely good or talented, from the word "death".
That's a def tag up you got there.
by TFS July 25, 2005
Def is when you're too lazy or your IQ is too low and you don't know how to properly write the word "Definitely".

So instead of looking uncultured and write shit like "Defenitely" or "Definetly" etc. you Def that shit and save yourself from embracements.
I'm def a retard
I'm def gonna beat my meat after writing this definition.
by Yung Iboprofen June 10, 2017
Word commonly used in place of "definetly"...most often heard when in the presence of Julie and Mandie
Julie- Getting drunk later, though?

Mandie- Def.
by Mandie February 19, 2005
"That is def the ugliest thing I've ever seen."
by Laurie *is hot* April 9, 2005
Short for 'defective', which means 'the Ultimate', superlative, better than good...

This started some time after Michael Jackson's "I'm Bad" video, in which 'bad', of course, meant 'good'.

So, to denote a meaning that means the ultimate superlative of 'good', people started using 'defective', which of course is the ultimate superlative of 'bad', and which then was simply abbreviated to 'def'.

Russell Simmons' Def Comedy Jam
by reality_bytes August 16, 2007
Old skool version of low it meaning forget it, dont bother or dont even go there but in a nice kinda way
man sez 'bruv, shall we jack the offie'
man&man 'nah def it, its too on top'
by moi&dem January 15, 2007