15 possible answers to
Answers with 3 characters: DIM Answers with 4 characters: DUMB Answers with 5 characters: CRASS DENSE DOPEY INANE THICK Answers with 6 characters: OAFISH UNWISE Answers with 7 characters: ASININE IDIOTIC MORONIC Answers with 8 characters: ANSERINE Answers with 9 characters: NITWITTED Answers with 10 characters: BONEHEADED