To crowd ones air up. To be so close to someone they have to smell your stinky ass. To be so close to someone they can see what you had to eat from all the crap on your teeth. To be so close to someone they can tell you are having an affair with GF because of that nasty smell on your breath....going down captain!
Yo back up you'z in ma breefin' space(e.g., breathing space).