(informal) An informal greeting.

(African-American Vernacular) What's up? What's going on?

(idiomatic) Used to add emphasis to “what” when beginning a question.

Considering what limited worth this advice, opinion, or suggestion might have for you; used to soften the presentation of unsolicited advice or information that may not be relevant.

(followed by a phrase) Regardless, in spite of. / (not followed by a phrase) Regardless of any or most possible adverse circumstances.

plural of what-if

Used to express regret or disappointment about an unfortunate event or piece of information.

Used other than figuratively or idiomatically: see guess, what.

(idiomatic) The latest developments in a particular situation or a person's life.

(informal) An informal greeting asking the other person what has recently happened in their life. A typical response might be "Not much; you?". The greeting is not always literal and may just be used to say hello.