A more thorough explanation:

Wash can have two different meanings:

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.

1. If you make $100 in income but also have a $100 deduction, your taxable income will be unchanged. This is an example of a wash.
2. After heavy rain, the river overflowed and deposited sand and rocks on the nearby land. This created a wash.

The first example illustrates the first definition of wash, where two effects cancel each other out. In this case, the gross income and deduction offset each other, resulting in no change in taxable income. The second example illustrates the second definition of wash, where the river deposits sand and rocks on the nearby land, creating a shallow area or arm of the sea.