This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. The state of being dumb (either mute or dim-witted), that is, not communicating vocally, whether from selective mutism or from an inability to speak.

n. Muteness, silence; abstention from speech.

n. Refusal or unwillingness to speak.

n. Show or gesture without words; pantomime; dumb-show.

n. The quality or state of being dumb; muteness; silence; inability to speak.

n. Muteness; silence; abstention from speech; absence of sound.

n. Incapacity for speaking; inability to utter articulate sounds. See deafness.

n. the quality of being mentally slow and limited

"Some have attributed the movie's success to a new cult of dumbness, which is just plain stupid: dumb is, and ever was."

stupidity   

oral language    vocal    deafness    speechless    speak    deaf and dumb    gesture    mutism    dumb    speech   

muteness    silence   

dumb   

scatology    sightlessness    woodenness    deafness    encephalopathy    coryza    sogginess    semi-consciousness    blankness    aurium