Definition of dumb

• 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"
• unable to speak temporarily; "struck dumb"; "speechless with shock"
• lacking the power of human speech; "dumb animals"