A "washer" is a small, flat, round object made of metal or rubber that is used with a screw or bolt. It helps to distribute the pressure and prevent damage between the screw or bolt and the surface it is being tightened against. Full definition
Our test car added a power sunroof for $ 850, headlight washer for $ 150, theft alarm for $ 250 and automatic transmission for $ 650. (articles.orlandosentinel.com)
Put laundry in washer before heading to out for the day. (crappypictures.com)