The act of washing one's face or hands (usually with water/soap); often appears as '洗面する' in formal contexts.
出かける前に洗面を済ませて身だしなみを整えた。
Before going out, I washed up and fixed my appearance.
病院の案内には『診察前に洗面してください』と書かれていた。
The hospital notice said, 'Please wash (your face/hands) before the examination.'
旅行先のホテルは洗面設備が充実していた。
The hotel at our destination had well-equipped wash facilities.