nutter, n. — Green’s Dictionary of Slang

nutter n.

1. a lunatic, an eccentric [nut n.² (1)].

1958		F. Norman Bang To Rights 36: The reason for this is to find out wether or not you are a nutter.
1962		B. McGhee Cut and Run (1963) 173: Nobody wants to antagonize a ‘nutter’.
1972		P. Fordham Inside the Und. 74: Ernie, always remembered as a ‘nutter’.
1989		R.G. Barrett Boys from Binjiwunyawunya 188: He’s a nutter [...] He used to go around chopping off people’s fingers with a meat axe.
1998		R.G. Barrett Mud Crab Boogie (2013) [ebook] Sooner or later he’ll pull that caper with a real nutter and wake up the next day in hospital.
1998		G. Burn Happy Like Murderers 326: Fuck off, you nutter! Fuck off out of it.
2005		M.B. ‘Chopper’ Read Chopper 4 142: I put together a crew of nutters never before seen in any prison.
2007		R. Milward Apples (2023) 68: I watched kids, workers and nutters walking.
2010		K. Richards Life 26: They were a bit more upper-class nutters - they got wheelchairs or something.
2015		I. Welsh Decent Ride 107: Ah’m hopin now that Sal’s no nutter wi a saviour complex.
2018		G. Gilmore Base Nature [ebook] ‘Davie, you nutter, that’s the only way to be successful’.
2021		P. Papathanasiou Stoning 92: ‘[T]hose religious nutters at the tourist park have a point’.
2021		Twitter 30 Nov. 🌐 The anti-mask nutters are getting their message in now.

2. the head [nut n.¹ (1b)].

1963

N. Dunn Up the Junction 20: So would I. Do me nutter in.

nutter butter (n.) [redup.; note brandname Nutter Butter, a form of peanut-filled biscuit]

(US campus) someone who is eccentric or absent-minded.

1996

Eble Sl. and Sociability 42: Examples of rhyme from college slang are [...] nutter butter ‘someone who is unaware or inattentive’.

nutter’s medo (n.)

(N.Z. prison) a tablet of largactil.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 127/1: nutter’s medo n. largactil, a largactil pill.