not bright

boring dim dumb simple slow sluggish stupid

addled low shallow

backward besotted brainless daffy daft dense dim-witted doltish feeble-minded half-baked ignorant imbecilic indolent insensate moronic numskulled obtuse scatterbrained simple-minded stolid thick unintellectual vacuous wearisome witless

active bright cognizant exciting intelligent interesting smart

clear eventful keen knifelike light lively luminous lustrous pointed quick sensitive serrated sharp vivacious witty