The addition of -ity to an adjective results in a shift of stress to the antepenultimate syllable; that is, words in -ity are stressed on the last syllable before the -ity, even in cases where this syllable is part of another suffix (as in words in -ability and -icity).
adjective, dumber, dumbest. 1. lacking intelligence or good judgment; stupid; dull-witted. 2. lacking the power of speech (offensive when applied to humans): a dumb animal.
(figuratively) Pointless, foolish, lacking intellectual content or value. This is dumb! We're driving in circles! We should have asked for directions an hour ago! Brendan had the dumb job of moving boxes from one conveyor belt to another. Lacking brightness or clearness, as a colour.