The condition of being unable or unwilling to speak

• Refusal to speak
• "The Heart is a Lonely Hunter" malady
• Inability to speak
• Inability to speak of misshapen summit

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Mutism \Mut"ism\, n. The condition, state, or habit of being mute, or without speech. --Max M["u]ller.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"state of being mute," 1824, from French mutisme (1741), from Latin mutus (see mute (adj.)).

WordNet Word definitions in WordNet
n. the condition of being unable or unwilling to speak

Wiktionary Word definitions in Wiktionary
n. A psychological disorder in which the sufferer cannot speak in certain situations.