Washboard

(n.) A fluted, or ribbed, board on which clothes are rubbed in washing them.

Washboard - Other Definitions

(n.) A fluted, or ribbed, board on which clothes are rubbed in washing them.
(n.) A board running round, and serving as a facing for, the walls of a room, next to the floor; a mopboard.
(n.) A broad, thin plank, fixed along the gunwale of boat to keep the sea from breaking inboard; also, a plank on the sill of a lower deck port, for the same purpose; -- called also wasteboard.