What is the meaning of Backwash?

A backward flow of water, as from oars, a propeller, breaking waves, etc.

The similar flow of air from an aircraft engine.

The result or consequence of an event; an aftermath.

The saliva, spit or food particles that have flowed back into a drink after someone has drunk from it.

The situation where economic growth in one area harms other areas by attracting people and business away from those areas.

washback

To operate a water filter in the reverse direction in order to clean it.

To affect with backwash.

To clean the oil from wool after combing.

Source: wiktionary.org