A fork of Rural Dictionary
a) somebody who will never pass you, but lingers way too close behind you. b) a tail-gater that fluctuates their speed dramatically on the highway just to piss you off or because they're on their cell phone. c) a tail-gater who might even pass you, but will eventually slow down and tail-gate someone else.
"Hey dude, check out this guy behind me. He's totally riding my ass!" "Aw man, I hate that. Pull over and let him pass." "Naw bro, I did let him pass me earlier, but he slowed down and now he's tail-gating me!" "Wow! What a bumper humper!" "Yeah man, and I totally have my cruise control on!"