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washing one's hands; water (or basin, etc.) for washing one's hands
restroom; lavatory; toilet
hand-washing (laundry, etc.)
食事の前に手洗をすませてから席に着く。
I wash my hands before sitting down for a meal.
手洗はこの廊下の突き当たりにあります。
The restroom is at the end of this hallway.
手洗の石鹸がなくなっていたので補充した。
The soap at the hand-washing station had run out, so I refilled it.