| adjective | slow to learn or understand; lacking intellectual acuity; ; ; - Thackeray “so dense he never understands anything I say to him” |
| adjective | temporarily incapable of speaking “struck dumb” |
| adjective | lacking the power of human speech “dumb animals” |
| adjective | unable to speak because of hereditary deafness |
| denseness | noun | the quality of being mentally slow and limited |
| dullness | noun | the quality of being slow to understand |
| dumbness | noun | the quality of being mentally slow and limited |
| obtuseness | noun | the quality of being slow to understand |
| slowness | noun | unskillfulness resulting from a lack of training |
| speechlessness | noun | the property of being speechless |
| mute | noun | a deaf person who is unable to speak |
| muteness | noun | the condition of being unable or unwilling to speak |