meaning "what do you
mean?"
it is a shortened version on "what are you going on about?" or "what are you
talking about?"
usually used when someone is not making sense for extended periods of time or if you feel like you've missed
something.
can be lengthened to show complete and utter confusion.
example 1.
knobhead: dude. i totally just pwned that
n00b. i asdfghjkl; the ask;nfw. fo shizzle my nizzle dizzle.
awesome: what you on about?
example 2.
knobhead: so, tomorrow, then?
awesome
person: what?
knobhead: we can go and you can meet them, yeah?
awesome
person: what you on about?
example 3.
Gavino Free(roosterteeth): what you on about?