Green’s Dictionary of Slang

1. rubbish, something annoying.

1966		D. Carpenter Hard Rain Falling 55: ‘Ratshit,’ he said distinctly. ‘What’er you bitchin about?’.
1973		C. Gaines Stay Hungry 136: Something about the card, man. Some ratshit about no card.
1979		(con. 1949) J. Hurling Boomers 70: This here’s a pile of shit! Ah’m goin’ to work for mah Uncle Willie. Maybe he can teach me somethin’ better’n this ratshit!
1983		J. Byrell (con. 1959) Up the Cross 13: ‘Sometimes I think that friggin’ zodiac [...] isn’t all ratshit’.
1985		L. Kramer Normal Heart [play script] How dare you still dispense this . . . this . . . this rat shit?!
1991		W.T. Vollmann Whores for Gloria 124: Was I talking bullshit or batshit or dogshit or was it just ratshit?
1994		G. Disher Crosskill [ebook] ‘That’s ratshit and you know it’.

2. an unpleasant or worthless person.

1974

(con. 1960s) R. Price Wanderers 59: Everything seemed incredibly boring and meaningless and stupid and fuck Joey anyway, the little bony rat, rat shit.