Synonyms of duller

1 Syllable
slow, low, daft, thick, dumb, dim
2 Syllables
simple, tedious, vacuous, witless, backward, dense, sluggish, stupid, doltish, shallow, addled, brainless, boring, daffy, stolid
3 Syllables
ignorant, half-baked, besotted, dim-witted, numskulled, moronic, obtuse, indolent
4 Syllables
imbecilic, wearisome, feeble-minded, simple-minded, insensate, scatterbrained
5 Syllables
unintellectual