Origionaly a description of one of those annoying little gnat flys that however much you try to swat it, hovers about six inch off yer snozzer(nose)....
Now apt for anything that gets too close, or in yer face, in an annoying way.
Any car that uses the two foot in front of your bumper as a gap to squeeze infront of you
Or the car that refuses to be overtaken... you try, and they speed up... when you slow down, so do they.
Any person that gets "In Yer Face", and wont go away.. especialy if they are doin' it on purpose...