Green’s Dictionary of Slang

1. (orig. US) a braggart, a boaster; a fantasist .

1971		T. Thackrey Thief 211: Boy [...] one thing to try and remember: never shit an old shitter.
1981		J. Elllroy Brown’s Requiem 70: ‘Don't shit a shitter [...] I want the truth’.
1998		K. Sampson Awaydays 4: There’s always loads of them, tattooed up and shitters to a man.

2. (orig. US) a term of abuse.

1983

S. King Christine 113: He was angry at what he called ‘the shitters’. Everything was the fault of ‘the shitters’. The shitters wouldn’t give him the promotion he deserved [...] the shitters put him in the stockade.

3. an exceptional example of something.

1979

S. King Dead Zone (1980) 223: I’ve got a shitter of a headache.

4. a male homosexual.

1990

H. Kureishi Buddha of Suburbia 18: My God, you’re a bloody pure shitter! A bum-banger! My own son – how did it transpire?