Green’s Dictionary of Slang

plug v.3

1. (US) to wager, to lay a bet.

[US]H. Blossom Checkers 20: It’s [i.e. horse-racing] an easy game to beat if you just stay off till you’re next to something good, and then plug it hard.

2. to advertise, to promote something, esp. when filtered through a TV or radio programme.

[US]Ade Artie (1963) 64: I would n’t like to start in and plug his game and then find myself on a dead one.
[Aus]Sydney Sportsman (Surry Hills, NSW) 27 Feb. 1/6: Recently his shop I entered, / Just as he was on the job / [...] /Pluggin’ of a certain cob.
[US]‘Billy Burgundy’ Toothsome Tales Told in Sl. 26: A reporter, who devoted much of his time [...] to plugging Elfie’s game.
[US]C. Sandburg letter 12 Sept. in Mitgang (1968) 137: This is not ‘plugging’ in any sense.
[US]J. Lait Broadway Melody 8: An entrenched battalion of burglars, sheiks, corruptionists, cake eaters, flask toters and theatrical heelers to plug it—and, presto!
[US]J.M. Cain Serenade (1985) 192: On your car, plug the horn, the lock on the gas tank, the paint job, the speed and the low gas consumption.
[US]B. Schulberg Harder They Fall (1971) 114: You go out and plug Molina like you never plugged anything in your life.
[US]Lait & Mortimer USA Confidential 166: Meanwhile it [i.e. a magazine] plugs those who turn handsprings for the underworld.
[UK]Mersey Beat 1–15 Nov. n.p.: The trouble is that they can’t plug a record properly.
[UK]N. Cohn Awopbop. (1970) 61: They paid fixed rates to get the songs plugged.
[US]Cab Calloway Of Minnie the Moocher and Me 44: You guys [...] beg me to plug one of your songs.
[UK]Guardian Guide 29 May–4 June 98: Look, I came here to plug a movie.
[US]W. Shaw Westsiders 74: Lonzo isn’t here to sign acts — he has his own product to plug.

In compounds

plug money (n.)

an illicit payment for promoting a record or song.

[UK]S. Jackson Indiscreet Guide to Soho 54: It is an open secret that many radio stars gladly accept ‘plug money’ for selling a song on the ether, despite the strict clause in their contracts.

In phrases

plug for (v.)

to act in support of, to make favourable statements about.

[US]C.L. Cullen Tales of the Ex-Tanks 375: Those tourists all plugged so hard for me that the [...] boss told me I could have the coach-driving job.
[US] K. McGaffey Sorrows of a Show Girl (2004) 31: Say, is it considered au fait for a bride-about-to-be to do a little plugging for wedding presents this early in the game?
[US]Ade ‘The New Fable of What Transpires’ in Ade’s Fables 146: He had to admit that Father was the only Outsider who seemed to be plugging for the Alliance.
[US]V. Samuels ‘Baseball Sl.’ in AS II:5 256: ‘Pluggers’ or ‘rooters,’ ‘plug’ or ‘root’ for their side or for their favorite players.
[US](con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 380: Fran would be so thrilled because she had plugged so much for it and took such an interest in the affairs of the sorority.
[US](con. 1941) C. Chessman Cell 2455 225: All the while I kept plugging for Chino.
[US]J. Bouton Ball Four 375: ‘I’m still plugging for you,’ Owens said. Bless him.