The action of holding out your smartphone while glancing between it and your surroundings frequently in order to have a sense of navigation much like a person using a compass. The most annoying cases is when the "compasser" is walking in a public settings and sometimes bumps into others or grins shamelessly at whatever is on their screen.
Compasser: *GRIN* LOL!
Dude 1: Watch out man, you spilled my drink!
Compasser: uh-huh, sorry... *GRIN*
Dude 1: Can you believe that asshole?
Dude 2: Yeah, what a dick.
Dude 1: Total compassing no-life.
In the subculture of marijuana slang, compassing is a tool used to assist a smoker who is using a pipe. The person who took the hit directly before the person who now has the bowl says, for example "Northeast," if the green is to the top right of the bowl (farther away from the smoker), or "Southwest," if the green is to the bottom left of the bowl (closer to the smoker).
Bob "Hey bro, I didnt get a good hit, can you give me a compass?"
Dave "Sure man, my last hit was Northwest."
Bob "Thanks! That was much better."
Dave "Don't thank me, thank whoever invented Compassing."