washer

A flat piece of material, often of metal and often an annulus, placed beneath a nut or at some joint, to distribute pressure, alleviate friction, provide directionally differentiated friction (e.g. making the nut turn counter-clockwise only with difficulty), or prevent leakage.

Something that washes; especially an appliance such as a washing machine or dishwasher.

A person who washes (especially clothes) for a living; a washerman or washerwoman.

A person who washes their hands compulsively, as a symptom of obsessive-compulsive disorder.

A face cloth.

To fit (a mechanical device) with a washer.