Definition from Wiktionary, the free dictionary
Alternative forms 
From the verb wash out.
washout (plural washouts)
- An appliance designed to wash something out.
- The cistern was fitted with washouts and air-valves.
- (biology, medicine) The cleaning of matter from a physiological system using a fluid.
- (meteorology) The action whereby falling rainwater clean particles from the air.
- A channel produced by the erosion of a relatively soft surface by a sudden gush of water.
- (colloquial) A disappointment or total failure; an unsuccessful person.
- As an actor, he was a complete washout, so he went back to accounting.
- A sporting fixture that could not be completed because of rain.
- The aerodynamic effect of a small twist in the shape of an aircraft wing
- To wash something out.