Short for "What What, in the butt". Originally from singer Samwell's song "What What (In the Butt)", whose viral music video was notorious for its references to anal sex and homosexuality. It has since been referenced in a South Park episode, where a video of Butters singing Samwell's song is posted on "Youtoob" by the boys.
Omg bby, ily we r bff's forever, ya rly, leik wwitb, hehe.
Internet shorthand for "what? what? in the butt", as coined on the animated television program "South Park".
I called Shanay and asked if she wanted to get down, whereupon she explained with a grin 'wwitb!'