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.
(..) Dialogue: Marked=..,Default,NTP,!Effect,Five points... Dialogue: Marked=..,Default,NTP,!Effect,...will be awarded to each of you... Dialogue: Marked=..,Default,NTP,!Effect,...for sheer dumb luck. Dialogue: Marked=..,Default,NTP,!Effect,Perhaps you ought to go.\Nlt might wake up. (..)2001 Harry Potter and the Sorcerer's Stone