She 'played/acted dumb' [=pretended to know or understand less than she really did] so we would assign her the easier tasks.
She thinks television is contributing to the 'dumbing down' of America.
Cutting training programs will 'dumb down' the American workforce.
(..) A figure like your father appears before them, and with solemn march goes slow and stately Whilst they, distilled almost to jelly with the act of fear, stood dumb and spoke not to him This to me in dreadful secrecy did they impart I knew your father, these hands are not more like (..)2015 Hamlet