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.
Dumb blonde is an unkind stereotype. The definition of a stereotype is a well-known idea or image of a person or idea that is held by a number of people. An example of stereotype is that blonde-haired women are dumb. Stereotype is defined as to attach an idea or image to a person who belong to a particular group.