dumbness (n.)

• aphasia
• aphonia
• asininity
• boorishness
• brevity
• briefness
• brusqueness
• conciseness
• crassness
• crudeness
• curtness
• deaf-muteness
• denseness
• density
• dimness
• dullness
• grossness
• hebetude
• laconism
• lethargy
• muteness
• mutism
• obtuseness
• opacity
• quietness
• quietude
• shortness
• silence
• slowness
• sluggishness
• sottishness
• speechlessness
• stolidity
• stupidity
• taciturnity
• terseness
• voicelessness