wash,n.1. A situation in which two effects offset each other. • For example, if an event produces gross income and also a deduction in the same amount so that taxable income is unchanged, the event creates a wash. 2. The shallow part of a river or the arm of a sea; the sand, rocks, and gravel washed down by a mountain stream and deposited on level land near the mouth of a canyon.
[Blacks Law 8th]