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)
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".