the uncool lazy way of saying "definitely"

Origin: " Definate "
" Def " : To strongly concur with a previously made statement.

short for definetly...

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.

short for definitions

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'.

take a shit, defecation