[adj] unable to speak because of hereditary deafness
[adj] lacking the power of human speech; "dumb animals"
[adj] unable to speak temporarily; "struck dumb"; "speechless with shock"
[adj] slow to learn or understand; lacking intellectual acuity; "so dense he never understands anything I say to him"; "never met anyone quite so dim"; "although dull at classical learning, at mathematics he was uncommonly quick"- Thackeray; "dumb officials make some really dumb decisions"; "he was either normally stupid or being deliberately obtuse"; "worked with the slow students"
dense, dim, dull, inarticulate, mute, obtuse, silent, slow, speechless, stupid, unarticulate