Dumber
adjective
Unable to speak; lacking power of speech (kept in "deaf, dumb, and blind").
“His younger brother was born dumb, and communicated with sign language.”
Silent; unaccompanied by words.
“dumb show”
(especially of a person) Extremely stupid.
“You are so dumb! You don't even know how to make toast!”
Synonyms: banal, brainless, dopey, ridiculous, silly, stupid, vulgar, dumbstruck