Green’s Dictionary of Slang

feeb adj.

feeble.

1987		in Delacoste & Alexander Sex Work (1988) 56: She couldn’t have taken another feebly dick, pink, hairy son of a bitch if he’s been shittin’ fifty dollars.
2001		N. Griffiths Sheepshagger 73: How’d me faverit fuckin half-wit then eh? The world’s best inbred backwoods feeb psycho mong?