Green’s Dictionary of Slang

1. (orig. US campus) of an object or person, unfashionable, unsophisticated; also as n.

1989		P. Munro Sl. U. 51: butter not cool, nerdy.
1992		R.C. Cruz Straight Outta Compton 77: Hey, man, that’s real butter!
2007		Skins ser.1 ep.3 [TV script] Hey, buttas, why you messin’ my flow?

2. of a woman, unattractive.

2001		Guardian G2 3 Aug. 3: The kids says that if you is butters you is ugly.
2003		BlazinParadise ‘Blazing Squad Language’ 🌐 Butters – A ugly thing or person.
2017		theculturetrip.com ‘Guide to London Slang 10 Jan. 🌐 Butters – ugly as hell.