Green’s Dictionary of Slang

plumbing n.

1. (orig. US) human internal systems, e.g. the excretory tract, the urinary system; the genitals.

[US] in W.C. Fields By Himself (1974) 475: Keep your plumbing warm on your trip East and return home soon and safely.
[Aus]D. Niland Big Smoke 118: [He] went inside only for meals and the functions of his plumbing.
[US]‘Paul Merchant’ ‘Sex Gang’ in Pulling a Train’ (2012) [ebook] You’re just a lousy lay, is all, or you got something screwed up in your plumbing.
[US]‘Iceberg Slim’ Pimp 96: A con ran a shiv into my plumbing.
[US](con. 1900s) G. Swarthout Shootist 105: Such was the state of his plumbing, he had to wait three or four minutes to achieve flow.
E. Shrake letter 29 July in Davis (ed) Permanent Wave 240: The instant the tequila hit the other garbage in my stomach I whirled and threw up [...] Anyhow, I have given the plumbing three days of rest again.
[US]H. Max Gay (S)language 32: Plumbing—male genitalia.
[UK]D. Lodge Therapy (1996) 94: I managed to produce a spurt of jism [...] so I know the plumbing is technically sound, but my cock is quite sore.
[US]J. Stahl Plainclothes Naked (2002) 5: At least the old skeek didn’t discuss his plumbing.
[Scot]T. Black Ringer [ebook] n.p.: Big Stauner’s the man, alright. Wouldn’t mind a piece of that. He looks a handy man. . . wonder if he’d take a look at my plumbing?
[Aus]T. Spicer Good Girl Stripped Bare i: As I spin around, I feel the ‘let-down’ and breastmilk almost squirts in his face. It seems there’s nothing dodgy about my plumbing.
M. Grossman Lost in Trans Nation 178: W]e are speaking of men and women who had perfectly normal plumbing prior to surgery.

2. (US) a trumpet, trombone, or similar wind instrument.

[UK]Vanity Fair (N.Y.) Nov. 71: plumbing: trumpet.
[US]Pic (N.Y.) 24 June 24: What Do You Know About Music? [...] 18. What instruments are sometimes referred to as ‘woodpile,’ ‘plumbing,’ ‘licorice stick,’ ‘88,’ ‘skins’?
[US]Cosmopolitan July 85: You with the plumbin’, what’s your name?
[US](con. 1940s–60s) Décharné Straight from the Fridge Dad.

3. fillings in teeth.

[UK]J. Thomas No Banners 117: The fillings in his teeth had been removed and replaced by unmistakable French ‘plumbing’ [OED].

4. (Aus.) the lungs.

[Aus]S. Maloney Brush-Off (1998) 81: You thrash about sucking in air and fill your plumbing with froth and foam until you choke.