1. (

• dense ,
• dim ,
• dull ,
• dumb ,
• obtuse ,
• slow

) 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" ;

2. (

• speechless ,
• dumb ,

) temporarily incapable of speaking; "struck dumb"; "speechless with shock" ;

3. (

• dumb ,

) lacking the power of human speech; "dumb animals" ;

4. (

• dumb ,
• mute ,
• silent

) unable to speak because of hereditary deafness ;