A smurf bite occurs when a constuction worker takes a shit in a port-a-potty, and gets the splash back effect of the blue chemical water directly in the asshole. When the shit hits the water, causing a splash of blue liquid, the splash goes due north and collides directly with a dirty, most likely hairy, ass hole.
Eric: Dude, I just took a shit in the johnny on the spot over there, and low and behold, smurf bite!
John: Ick, I spray shit in that thing about 20 minutes ago.
Eric: I thought I notices two shades of brown on the toilet paper. Sick.