1 definition by Dr. Impossible
To assert oneself in a particularly obnoxious way without warning or permission. Originally from a Canadian "mockumentary" on the extreme sport of backjumping, in which helmeted participants score points by leaping on the backs of unsuspecting pedestrians, scoring points based on the length of the "ride" and the poise displayed in avoiding arrest or assault by the "back". Seems to have passed into more common use when reports surfaced of viewers of the mockumentary actually performing these stunts.
by Dr. Impossible November 22, 2003