play dumb

play dumb (third-person singular simple present plays dumb, present participle playing dumb, simple past and past participle played dumb)

1. To pretend to be mute.
   • 1904, Rex Ellingwood Beach, "The Mule Driver and the Garrulous Mute," in Pardners,

     I played dumb 'cause I knew if I talked at all, being simple and guileless, you all would twist me up and have the whole thing in a jiffy.

2. (idiomatic) To pretend to be slow-witted or lacking in specific knowledge, usually in order to avoid responsibility or to gain some advantage.
   • 1966, "Milestones," Time, 1 Apr.,

     Died. Virginia Hill, 49, redheaded, free-spending playmate of the underworld . . . who later acted out a cameo role before the late Senator Estes Kefauver's Senate crime committee, playing dumb about the business dealings of her many racketeer friends.