dumbs down

Synonyms:
2, 3. Dumb, mute, speechless, voiceless describe a condition in which speech is absent. Dumb was formerly used to refer to persons unable to speak; it is now used almost entirely of the inability of animals to speak: dumb beasts of the field. The term mute is applied to persons who, usually because of congenital deafness, have never learned to talk: With training most mutes learn to speak well enough to be understood. Either of the foregoing terms or speechless may describe a temporary inability to speak, caused by emotion, etc.: dumb with amazement; mute with terror; left speechless by surprise. Voiceless means literally having no voice, either from natural causes or from injury: Turtles are voiceless. A laryngectomy leaves a person voiceless until he or she has learned esophageal speech.