Washouts

noun

1. An appliance designed to wash something out.

   "The cistern was fitted with washouts and air-valves."

2. The cleaning of matter from a physiological system using a fluid.

   "a bladder washout"

3. A period between clinical treatments in which any medication delivered as the first treatment is allowed to wash out of the person before the second treatment begins.
4. The action whereby falling rainwater clean particles from the air.
5. A channel produced by the erosion of a relatively soft surface by a sudden gush of water.