Noun

1. An act of washing something out, or an appliance or device for doing so.

   The cistern was fitted with washouts and air-valves.

2. The cleaning of matter from a physiological system using a fluid.
3. The action whereby falling rainwater clean particles from the air.
4. A channel produced by the erosion of a relatively soft surface by a sudden gush of water.
5. A disappointment or total failure; an unsuccessful person.

   As an actor, he was a complete washout, so he went back to accounting.

6. A sporting fixture that could not be completed because of rain.
7. The aerodynamic effect of a small twist in the shape of an aircraft wing