Green’s Dictionary of Slang

suit n.1

[SE suit, a full set of clothes]

1. a gold watch and seals.

[UK]C. Hitchin Conduct of Receivers and Thief-Takers 15: A Suit, alias Gold-Watch, or two or three Cloaks, alias Gold-Watch Cases.
[UK](con. 1715) W.H. Ainsworth Jack Sheppard (1917) 141: A fence, or receiver, bargaining with a clouter, or pickpocket, for a suit — or [...] a watch and seals.
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Sl. Dict.
[Aus]Crowe Aus. Sl. Dict. 82: Suits, watch, chain and seals.

2. (US) a plainclothes detective.

[US](con. 1946) G. Pelecanos Big Blowdown (1999) 70: The suits they got on the case, they haven’t turned up a thing.
B. Hubbard Substantial Evidence 162: The case had been assigned [...] to Ronnie Goolsby, one of the ‘suits’ in our division.
[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 181/1: suit n. 2 a detective .
[US](con. 1972) Jurgenson & Cea Circle of Six 13: Chief of Detectives Albert Seedman—my boss. He entered the mosque, followed by three other unrecognizable suits.

3. (also gray-suit, three-piece suit) a member of management, a businessman, anyone who has to wear a suit for their daily work, as opposed to more casually dressed creative or freelance workers, or those in jobs that in any case have no need for suits; thus an uncreative, authoritarian person.

[US] ‘Hot Rod Lexicon’ in Hepster’s Dict. 25: The gray suit look like he had a lot of money.
[US]W. Murray Sweet Ride 152: One of the rumpled suits began to cry.
[UK]J. Carr Bad (1995) 66: When some gray-suit asked me which trade, I replied ‘butchery’.
[US]Eagle (Bryan College Station, TX) 12 June n.p.: He [.e. Robert Blake] tells [Dan] Rather and producer Igor Oganesoff that it the network ‘suits’ (i.e. executives) don’t like the way he’s doing the show,, they can ‘take me off the air’.
[UK]J. Sullivan ‘Christmas Crackers’ Only Fools and Horses [TV script] Standing near Del is Earl, another three-piece suit.
[US]C. Stroud Close Pursuit (1988) 138: You tell me I have to take a call from a pair of college-boy suits from IAD! No fucking way, sir. [Ibid.] 151: I think the guy wishes he’d never so much as waved at one of those three-piece suits from Justice.
[US]Eble Campus Sl. April.
[Ire]P. Howard The Joy (2015) [ebook] Fuck bosses and career ladders and stress and kissing some suit’s arse every day.
[UK]Indep. Rev. 10 July 20: The starchy bunch of suits in charge at British Airways simply can’t get it right.
[Aus]R.G. Barrett Wind & Monkey (2013) [ebook] [T]wo men in jackets talking to another suit further on the left who had to be cops.
[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 181/1: suit n. 1 = white-shirt .
Kanye West untitled track on College Dropout [album] 🎵 I don’t listen to the suits behind the desks no more.
[Aus]L. Redhead Cherry Pie [ebook] The suit, balding and pasty, sat in one of the low chairs.
[UK]J. Niven Kill Your Friends (2009) 29: A couple of Frog suits decided it would be cool to have a little convention in the South of France.
[Aus]D. Whish-Wilson Zero at the Bone [ebook] He struck a suit who’d stared too long, knocked him on his fat arse.
[US]D. Winslow The Force [ebook] The suits had to grin and bear it.
[UK]M. Herron Joe Country [ebook] [S]uits’ bodies were easier to find than those of joes.
[US]D. Winslow ‘The Last Ride’ in Broken 317: The suit from Homeland Security took over.
[Aus]C. Hammer Opal Country 89: ‘Who’s the suit?’.
[UK]R. Milward Man-Eating Typewriter 69: I savvied [...] twas a specjalni privilege [...] being dragged in before the Governor and the suits.

4. (US police) a bribe, in 1968 of $100.

[US]G. Astor N.Y. Cops 164: ‘You should meet the captain [...] ‘And make me and yourself look good. Give him a hat.’ The price of hats varies with the state of the economy and in 1968 was supposedly worth $20 while a ‘suit’ sold for $100 and a pack of cigarettes for $5 .

SE in slang uses

In phrases

suit up (v.)

to dress oneself in a suit or uniform.

[US]C. Heath A-Team 2 (1984) 91: Let’s get ahold of Schaeffer and suit up.
[US]A. Rodriguez Spidertown (1994) 67: Pretty soon, he’d suit up [...] dress up in a three-piece suit and appear on Donahue.
that suit won’t fit

that is unacceptable; that will not work or ‘go’.

[UK]‘Nocturnal Sports’ in Universal Songster II 179/2: Vhat are you hup to with that there vench. That there’s my vide, rum ’un, so that suit vo’n’t fit, you see. I sees vhat you’re arter, but that cut vo’n’t do, demme.