It is one of the more subtle ways of telling annoying bragging people to fuck off. You don't really mean it, nor you care about their success and you want them to get out of your sight or at least change the topic.
It can also be accompanied by 👍 (4fingers) 👉 gesture for maximum effect
Random Douchebag: Hey I aced that calculus exam the other day, still don't know how you managed to fail it.
You: Gud 4 U!(👍 (4fingers) 👉 )
Easy way to ask a female if she is "d" or ready to perform "rj", which is an oral sexual pleasure upon the anus and rectum of the male receiving the "rj". This is an incredibly easy 6 letter sentence most commonly used by the Los Angeles underground youth in the early 20th century.
Boy: (Just hit with a text letting him know she's home alone) Whatsgood bitch.
A phrase indicating or implying that the person who released these words is better than you at just about everything and that you are about to "get rekt" (another term implying that someone has absolutely raped you at whatever activity you are competing in)
Sorry bro, you can't join my clan, i'm way 2 MLG 4 U.