Green’s Dictionary of Slang

(a) a reckless gambler.

1868		Sydney Punch 19 Sept. 135/2: Hurrah for the Randwick Races [...] Where never a ‘crack’ was nobbled, Nor a ‘plunger’ showed his face.
1869		Man about Town 25 Sept. 22/3: [T]he severe panic brought about by the plungers has not yet run its course.
1870		Illus. Sydney News 17 Feb. 3/3: The word ‘plunger,’ to represent a gentleman of fast habits, is in common use; ‘going the pace,’ and ‘taking a cropper,’ are gradually being admitted in small talk.
1876		World (N.Y.) V. No. 115. 4: The prince of plungers, with hat jauntily cocked over one eye .
1879		Sporting Times 1 Mar. 3/2: Endeavouring to turn retrevor of my fortunes by becoming a plunger.
1881		Bulletin (Sydney) 5 Feb. 5/1: A ‘plunger’ lost £1100 on the late Auckland races.
1882		Nat. Police Gaz. (NY) 23 Sept. 3/4: F.T. Walton, the Plunger [...] has been raising old Cain on the American turf this season.
1883		E.J. Milliken Childe Chappie’s Pilgrimage 18: Hail, glorious Goodwood! Thy promise afar / Gives hope to the Plunger.
1884		Ally Sloper’s Half Holiday 24 May 25: I’ve made up my mind I’ll be a plunger. Fellows I know have said, ‘Alexander, don’t’.
1890		Sporting Times 1 Mar. 2/3: I’m no plunger, / But I’ll gamble the whole of my stock ; / That there isn’t a horseman can beat him, / Be he gentleman rider or jock.
1895		Harrington & LeBrunn [perf. Marie Lloyd] He knows a Good Thing When He Sees It 🎵 My brother’s a plunger - has quids on a horse.
1895		Coburg Leader (Vic.) 11 May 4/5: That Paddy W. Down East is a heavy plunger at Uchre. Sling that game and chop wood, Paddy.
1896		F. Hutcheson Barkeep Stories 84: [D]e suckers went down the line like a couple o’ reg’lar plungers.
1903		A. Binstead Pitcher in Paradise 56: Plungers of all sizes will ever receive a steady welcome from the Ring.
1904		Sun. Times (Perth) 17 Jan. 2/3: he was one of the greatest plungers the turf has known.
1907		Sun (NY) 24 Feb. 8/3: The game’s been tying a can to me since Dave Gideon was a $2 plunger.
1910		‘Doss Chiderdoss’ ‘The Old Year’s Failures’ Sporting Times 1 Jan. 1/3: What of Plunger’s resolve to let gee-gees alone, / And to never more bet on a race?
1913		Sport (Adelaide) 27 Sept. 4/1: Ponto H., the Jubilee plunger, has got [a] good thing for Saturday .
1919		T.A. Dorgan in Zwilling TAD Lex. (1993) 32: (IS: Trying to work as the office plungers exchange stories of big wagers on the merry-go-round).
1920		Ade Hand-made Fables 84: There is Jimmy Hooper, supposed to be the nerviest Plunger on the Exchange. He can lose or win a Million without disturbing the Ash on his Cigarette.
1930		W.R. Burnett Iron Man 189: ‘I won a hundred dollars on that bum,’ said Mandl. ‘You plunger,’ said Regan.
1940		D. Maurer Big Con 41: The mark always feels like a piker instead of a plunger.
1953		A.J. Liebling Honest Rainmaker (1991) 57: George Smith, the famous race-track plunger [...] sometimes bet a hundred thousand dollars on a race.
1956		‘Toney Betts’ Across the Board 168: Riley Granon, Davy Johnson, and other bygone plungers.
1966		J. Holledge Great Aust. Gamble 13: [F]ew of the big-time plungers of the Australian turf have finished very far in front when they concluded their struggle with the books.
1974		G. Mayer Bookie 140: He made $10 ninnies into $100 plungers, conservative bettors into rubber-band-off-the-bankroll monsters.
1999		G. Seal Lingo 147: Other cheats were those who [...] organised catch-bets in which a decoy bet was made to entice a flat, or plunger (both fools and easy marks) to place a losing bet.

(b) in fig. use, anyone who takes risks.

1885		Bulletin (Sydney) 21 Mar. 6/4: From first to last, Mr. Dalley’s career as a statesman has been that of a bold political ‘plunger.’.
1910		Spokane Press (WA) 27 Mar. 5/3: It would hardly be fair to divulge the enterprising old ‘plunger’s’ name.
1914		Ade ‘The New Fable of the Aerial Performer’ in Ade’s Fables 195: As a rule, the tall-grass Plunger [i.e. stock investor] with a wad of new Kale has about the same per centage in his favor as that enjoyed by a Shoat out at the well-known Establishment of Armour & Co.

(c) (US campus) a spendthrift.

1997–2000

Da Bomb 🌐 22: Plunger: Overspender.

(a) the penis; thus plunger-pumping, sex.

1997–2000

College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Plunger pumping {offensive} (noun) Gay sex.

(b) (US gay) an energetic, speedy copulator.

1972

B. Rodgers Queens’ Vernacular 90: men who fuck hard and fast [...] plunger.

(c) (US black) a ‘strap-on’ dildo, as used by a woman to simulate heterosexual intercourse or anal sex.

2018

Young M.A. ‘I Got the Bag’ 🎵 Treat the pussy like a plumber nigga, put my plunger in it she screaming.