Green’s Dictionary of Slang

1. (US) a fool.

1906		Inter-Ocean 5 Aug. 21: The mush scratched checks [...] as he needed them .
1920		E. O’Neill Anna Christie Act I: You’re an old mush!
1968		A. Diment Bang Bang Birds 57: So this mush is running a string of [...] houses of ill-repute.

2. (also moosh) a man, a ‘chap’; thus as a term of address or greeting, e.g., Oi! Mush!

1936		J. Curtis Gilt Kid 53: When I bash a bloke he gets bashed. I’m a bit of a coring mush, myself.
1947		J. Maclaren-Ross Of Love And Hunger 32: ‘No one in, mush,’ he said in a low, hoarse voice. [Ibid.] 34: Mush, whatever you do don’t join the bleeding army.
1958		D. Reeve Smoke in the Lanes 31: He’m an ole beardy mush, like me Uncle ’Lijah.
1960		(con. WWII) R. Leckie Marines! 136: ‘Mush, you big mushhead, you — mush,’ I said!
1972		Galton & Simpson ‘Live Now, P.A.Y.E. Later’ Steptoe and Son [TV script] If you do that again, mush, I’ll . . .
1988		Beano Special No. 4 n.p.: Oi! Watch it, Moosh! Not so rough!
1989		P. Manning ‘Sl.’ in Kray (1989) 62: To understand Romany you must be able to chant the can / A bory mush is a governor and a roy is a gentleman.
1996		S. Bell If... 27 Nov. in If Files (1997) 116: ’Ow old are you, moosh?
1998		M. Newall ‘Sir Gawayne and the Grene Knight’ in Indep. Weekend Rev. 26 Dec. 1: I knowe the mushe you’re aftere. A ryghte yaa-hoo.
2005		B. Hare Urban Grimshaw 45: I asked her her name. ‘Kara MacNamara [...] Don’t wear it out, mush.’.
2024		J. Meades Empty Wigs (t/s) 99: Free and easy, that's the way Mush.

3. (UK, Liverpool, also moosh) a prostitute’s client.

1980

J. McClure Spike Island (1981) 133: I had old lady [...] sayin’ she was fed up being pestered by the mooshes every time she went out.

4. an outsider.

2005

B. Hare Urban Grimshaw viii: Mush Outsider. [Ibid.] 91: He’s not a mush [...] He’s sorted. he’s one of us.