Definition of "nutter"

That bird who's hanging' out with you is mad like cat piss / Like bread and jam, or a knife going with butter / Face it son, your missus is a nutter!

2005, “Your Missus Is A Nutter”, performed by Goldie Lookin Chain

When I asked Mr Robinson why he'd made his own attempts, he said, 'It gets to be a bug. And I suppose I'm a nutter.'

2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, page 268

Nut Butter (Table Nutter) is also recommended.

1907, Reuben Swinburne Clymer, The International System of Direct Medication, page 223

Among the miscellaneous articles examined, 27 samples of vegetable fat resembling lard were purchased for analysis under the various names of nut lard, nut butter, nutter, palmine, &c. These were passed as genuine.

1910, Great Britain. Local Government Board, Annual Report, number 39, page xci