OED2: wash-out [mit Bindestrich]
1. a. An act of washing out a cistern, etc.; a pipe or other appliance for doing this. Also attrib.
b. Biol. and Med. The removal of material, esp. from a physiological system, by means of a fluid; the fluid used for, or matter removed by, this.
c. Meteorol. The removal of particles from the air by falling water droplets. Cf. rain-out 2.
2. Mining. A place where a portion of a coal or ironstone seam has been carried away by a stream, a deposit of sandstone being left in its place.
3. The removal by flood of a portion of a hillside; a hole or breach in a railway or road track caused by flood or erosion. Orig. U.S.
a. A disappointing failure, a sell.
b. A useless or unsuccessful person; spec. in Air Force slang, a person who is eliminated from a course of training.
c. Air Force slang. A wrecked aeroplane.
5. Aeronaut. A decrease in the angle of incidence of an aeroplane wing towards the
Merriam-Webster: washout [ohne Bindestrich]
1.a washing out of earth, gravel, etc., by water, as from an embankment or a roadway by heavy rain or by a flash flood.
2.the hole, break, or erosion produced by such a washing out.
3.Also, wash'-out'. Aeron. a warp in an airfoil that gives a decrease in the angle of attack toward the tip. Cf. washin.
5.Informal. an utter failure.
6.Informal. a person who has failed a course of training or study: air force washouts.