adv: really really really cool, or sick.
A: Yo, that beat was dagnasty awesome!
B: You know it!
honestly; seriously. Derives from and sounds like the phrase "for serious?" Variation on "for real?"
synonym: "fo sho"
Person 1: I heard so-and-so is getting fired.
Person 2: for real?
Person 1: for CEreal.
Person 2: wow...that's some harsh stuff.