An extremely annoying question that has started to overtake 'Hi' and 'Hello' as a casual greeting.
Urban Dictionary definition:
An extremely annoying question that has (unfortunately) replaced "Hello" or "Hi" as the most popular form of casual greeting. For full effect, best delivered while walking past someone at about 90 m.p.h. so the person you're talking to has no time to respond, and in a tone that suggests you really don't give a sht about "what's up" with them.