Green’s Dictionary of Slang

throbbing gristle n.

[gristle n.]

the penis.

[Aus]G. Seal Lingo 88: The extent and variety of the Lingo terms for genitals and other body areas hints at a determined, if perverse, use of euphemism to avoid the use of perfectly respectable words like testicles, penis, vagina, and posterior. Such terms, though, seem sterile and colourless to the Lingoist who prefers such delights as [...] prick, dick, [...] throbbing gristle, trouser snake.