wash·out / ˈwäshˌout; ˈwÃ´sh-/ • n. 1. [usu. in sing.] inf. an event that is spoiled by constant or heavy rain. ∎ a disappointing failure: the film was a washout.2. a breach in a road or railroad track caused by flooding. ∎ Geol. a channel cut into a sedimentary deposit by rushing water and filled with younger material.3. Med. the removal of material or a substance from the body or a part of it, either by washing with a fluid, or by allowing it to be eliminated over a period.