Backwash

1. In uranium leaching, flushing from below of colloidal slime from ion exchange column after adsorption cycle. The cleaning of sand filters.
2. Water or waves thrown back by an obstruction such as a ship, breakwater, cliff, etc. AGI
3. The return flow of water seaward on a beach after the advance of a wave. See also: backrush

Source: Dictionary of Mining, Mineral, and Related Terms