Def For Sure 

When someone asks you to do a favor, and you don't plan on doing it, you say def for sure and gradually walk away like nothing happened

Rebensaltz: I'm failing Chemistry, do you think I can take a picture of your notes?
Ray and Ed: Yeah def for sure man, I'll def hit you up with that!

Def For Sure by ZROSENEDI May 12, 2016

For Def Sure

When simply saying 'yes' just isn't good enough. It's like saying yes, but X10. Usually used with an exclamation point

Kat: I'm so hungry
Reuben: Do you wanna get some Chinese food?
Kat: For def sure!

For Def Sure by Kitty Kat Wants Your Soul March 30, 2008