Backwash

The word Backwash may refer to:

Backwash (geography), the water that rolls back down a beach after a wave has broken
Backwash (physical phenomenon), the backwards flow of air or water
Backwash, the process of thoroughly cleaning a pool filter pump by reversing the flow of water through it with the dirt and rinse water going to waste.
Backwash (The Wire), an episode of the HBO television series The Wire
Backwash (album), a retrospective compilation by the group Talulah Gosh
The liquid that flows back into a drinking glass from one's mouth.