noun
sake cup rinsing bowl
A small bowl or vessel used in traditional sake service for rinsing sake cups (ochoko) between pours. Also referred to as 杯洗 (さかずきあらい).
See also: 杯洗
料亭では、杯洗いに水を張ってお猪口をすすぎます。
At traditional Japanese restaurants, they fill the cup-rinsing bowl with water and rinse the sake cups.
Same meaning; 杯洗 is a shorter kanji form, while 杯洗い includes the okurigana い.
Compound of 杯 (さかずき, 'sake cup') and 洗い (あらい, 'washing'). The exact historical derivation is uncertain, but the word transparently describes its function.