Synonyms to lamebrained

Boeotian, asinine, beef-brained, beef-witted, blockish, bovine, chumpish, cloddish, cowish, crass, dense, doltish, dullard, dumb, duncical, duncish, fat, gross, ineducable, klutzy, lumpish, oafish, opaque, sottish, stupid, thick, unteachable, wrongheaded