Green’s Dictionary of Slang

plug-ugly n.

[proper name Plug-Uglies, a New York (and Baltimore) street gang of the period. The origin of the name is debatable. One suggestion is that they were named after the large plug-hat n. (1), stuffed with paper, that each member wore for protection from the clubs of such opponents as the Dead Rabbits or the Bowery Boys; alternatively f. SE ugly + plug, a face, or, as a correspondent of The Times (4 Nov. 1876), writing of the Baltimore variety, suggested, ‘it was derived from a short spike fastened in the toe of their boots, with which they kicked their opponents in a dense crowd, or, as they elegantly expressed it, “plugged them ugly”’]
(orig. US)

1. (also pug-ugly) a thug, a violent person; also attrib.

[[US]Ladies’ Repository (N.Y.) Oct. VIII:37 316/2: Plug, A a nickname for a homely man].
Butte Record 29 Nov. 3/7: The [...] Plug Uglies [...] went down to Philadelphia on election day, [...] to fight off and whip the democracy from the polls [DA].
[US] letter in Silber & Sievens Yankee Correspondence (1996) 56: What I want to see done is, that if Baltimore makes any farther resistance to the passage of troops through her streets, that bloody ‘Plug Ugly’ city cleaned up!
[UK]G.A. Sala My Diary in America I 153: An ‘extra’ of the New York Plugugly and Staten Island Shoulder-hitter may announce that Charleston has fallen.
[US]J. O’Connor Wanderings of a Vagabond 195: He belonged to that political class which for many years ruled Baltimore with pistols, knives, brass-knuckles, and slung-shots, known as ‘Plug Uglies,’ among whom he was a kind of leader.
[US]C.F. Lummis letter 15 Sept. in Byrkit Letters from the Southwest (1989) 4: A youthful looking Plug Ugly [...] emerged from the crowd with a ‘be-Jesus’ swagger.
[US]S. Crane Maggie, a Girl of the Streets (2001) 53: She goes off with that plug-ugly who looks as if he had been hit in the face with a coin-dye.
[Aus]Sydney Sportsman (Surry Hills, NSW) 6 Mar. 4/1: Boxing [is] to be left as the plaything of the plug-uglies of our city .
[US]A.H. Lewis Boss 64: I defy both you and your plug-uglies.
[US]J. London Valley of the Moon (1914) 242: He’ll kill somebody yet, that plug-ugly.
Wodehouse ‘Jeeves and the Chump Cyril’ in Death at the Excelsior [ebook] [T]he rummy-looking plug-ugly who was now leaning against a potted palm.
[US]S. Lewis Babbitt (1974) 247: I do think he ought to stand right up and bawl out those plug-uglies to a fare-you-well!
[US]J. Lait Gangster Girl 97: The plug-ugly who was guarding Alice Schuyder in Silk Freeman’s windowless apartment turned from the door and pushed it shut.
[UK]R. Westerby Wide Boys Never Work (1938) 53: Don’t you think people are [...] frightened by having to salute every plug-ugly in uniform that looks ’em over.
[US]C. McKay Gingertown 130: I get a feeling that you really like that great big plug-ugly.
[US]W.D. Overholser Buckaroo’s Code (1948) 66: I saw you ride into town with Harriman and his bunch of plug-uglies.
[US]Murtagh & Harris Who Live In Shadow (1960) 20: He’s no plug-ugly. He’s your pal.
[Aus]L. Haylen Big Red 8: Charges of rustling and sheep stealing, strong arm action by the squatters’ hired plug-uglies all shot back into the memory of the men.
[US]‘Troy Conway’ Cunning Linguist (1973) 53: [H]e now had an explanation for the strong-arm plug-ugly who had been found by the armed guards, sleeping it off in the office.
[UK]F. Norman Too Many Crooks Spoil the Caper 69: Tools Gunstone and several of his plug-uglies were lounging in wooden chairs around a potbelly stove.
[US]H. Rawson Dict. of Invective (1991) 304: plug-ugly. A ruffian.

2. a professional boxer.

[US]O. Kildare Good of the Wicked 23: ‘Ah, what’d you know about it?’ growled the plug-ugly. [...] ‘If them referees wasn’t crooked, I’d been a champeen long ago.’.
[Aus]Bulletin (Sydney) 30 July 10/1: Lengthy cables to our papers, [...] / Tell of London crowds self-harnessed / To the carriages of boxers, / Tell of frantic street-ovations / Tendered freely to ‘plug-uglies’ / (As the D.T. used to put it).

3. an extremely unattractive person.

[US]L.W. Payne Jr ‘Word-List From East Alabama’ in DN III:v 358: plug-ugly, n. An ugly person or thing, especially an ugly horse.
[UK]Wodehouse Inimitable Jeeves 91: The rum-looking plug-ugly who was now leaning against a potted palm.
[US](con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 100: Studs [...] wondered who old plug-ugly was.
[US]Murtagh & Harris Cast the First Stone 212: I know [...] some plug-uglies who can just electrify the boys.
[US]R.D. Pharr S.R.O. (1998) 272: [I was] really peeved at the idea of anybody thinking those two plug-uglies could be anything to me.
[UK]Guardian G2 9 Feb. 13: Crowds of plug-uglies yelling at each other.

4. a carnival float.

[US] in A. Banks First-Person America (1980) 17: In the afternoon we had what we called the ‘plug-uglies’ —funny floats and clowns who took off the political subjects of the day.