look up any word, like b4nny:
 
1.
the combination/compound word - that's wassup-for real/rizzle. Implying to "subject" intended to be incredibly awesome or amazingly cool, etc.
"Hey brah! There's this party at "so and so's"! You wanna come?" - "Hell yeah! That's forsup!"

or

"Dude, check out this nug!" - "Holy fuck, thats forsup!"
by JamesPaiva March 07, 2010