One of the dozens of slang terms used by Beavis and Butt-head. Buttknocker could refer to
a)A homosexual, as anal sex is the only form of intercourse for gay men, or
b)An erection in somebody's ass, referring to pulling out and then tapping and wiping the semen on said ass.
Beavis: Shut up, Butt-head! I'm gonna play drums on your nads with my foot!
Butt-head: I'd like to see you try, buttknocker!
Beavis: Don't call me that, Butt-head! (Beavis kicks Butt-head in the testicles)
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.
I had a trucker's tan after driving for 10 straight hours on a sunny day.