When the male's penis head is swollen or engorged by oral sex, he has had his knob polished. In actuality, though, "get my knob polished" has come to mean "get a blow job" with the hope of orgasm included.
The term is not to be confused with "dip my wick," another penile reference that usually implies penile-vaginal or even penile-anal sex.
A person who does not orally polish the knob but instead leaves it messy with saliva and/or pre-ejaculate is a knob slob.
--"Don't look at me, bro. Find your own head."
2. --"I like to polish his knob 'til it's real shiny and red!" - one of the "two gay guys from Jersey" (Fred Armisen, Bill Haider) on TV show Saturday Night Live.