Green’s Dictionary of Slang

1. (US) a male homosexual transvestite prostitute.

1979		E. Torres After Hours 60: Couldn’t find a hooker or a teevee knobber on 44th and Eighth.
1989		J. Morton Lowspeak.
2000		P. Howard Miseducation of Ross O’Carroll-Kelly (2004) 199: My old pair still think I’m a knobber.

2. (US campus) fellatio.

1989

P. Munro Sl. U.

3. (US) a stupid, obnoxious person.

1991

Vancouver Sun 12 Dec. D8: I won’t look like a knobber crusing [sic] this [HDAS].

4. (US) the penis; usu. in phr. below.