Green’s Dictionary of Slang

a general epithet of abuse.

1961		N. Mailer Advertisements for Myself 22: We’re a nation of [...] homosexuals, hoodlums, fart-faced Southern governors [etc].
1977		Maledicta 1 (Summer) 7: Some day, we may be able to freak out our fartfaced colleagues with Maledicta Lives! T-shirts.
1979		D. Maitland Breaking Out 169: You are a bloody lop-eared [...] pig-headed, fart-faced flip of a fucking galah!
1981		D. Barthelme ‘The Glass Mountain’ Sixty Stories (2003) 173: Fart-faced fool.
2008		C. Hardyment Dream Babies 295: I noted ‘fart-faced, roly-poly fluffy po’ on Mumsnet before the present ban.