dumb

aphonic banal blockheaded brainless denser dense dimmer dim dim-witted dimwitted dizzy doltish dopey dumbfounded dull duller empty feeble-minded half-baked hushed idiotic inarticulate incoherent incommunicable incommunicative inobtrusive insensate moronic most vacuous oafish obtuse quietened quieter quieten quietest quiet reeling retarded shush silent silence simpleminded simpler simple slow slowest slower speechless stolid stupid taciturn thickheaded thick-witted thick tight-lipped tightlipped uncommunicable unintelligent vacuous voiceless voiceless witless zany