Green’s Dictionary of Slang

dumbshit adj.

(US) stupid.

1978		R. Price Ladies’ Man (1985) 197: I flashed on sitting in the high school auditorium with a bunch of guys watching some dumb shit movie.
1986		L. Heinemann Paco’s Story (1987) 80: I mean some godawful dumbshit nigger stunts.
1989		(con. 1968) W.E. Merritt Where the Rivers Ran Backward 268: Those dumb shit enlisted men never listen to a thing you say.
1998		R. Unterberger Unknown Legends of Rock ’n’ Roll 304: Being pretty much an average dumbshit Spinal Tap type-pop musician, I was interested in haircuts, girls, drugs, and quite a lot of music.
2005		C. Mazza Many Ways to Get It, Many Ways to Say It 184: What a dumshit mistake.
2012		T. Piccirilli Last Kind Words 157: Look at who the Rands are going to welcome into the fold—this dumbshit poser.
2020		C. Hiaasen Squeeze Me 113: ‘Where’s your dumbshit partner?’.