water-hammer

n [U] knocking noise in a pipe when water is turned on or off 水锤现象, 水击作用（水龙头开或关时水管发出的打击声）.

watchmaker, watchman, watchword, water, water point, water polo, water ski, water-bed, water-bird, water-biscuit, water-borne, water-bottle, water-buffalo, water-butt, water-cannon, water-closet, water-colour (US -color), water-cooled, water-diviner, water-fowl, water-hole, water-ice, water-jump, water-level, water-lily, water-line, water-main, water-meadow, water-melon, water-mill, water-pistol, water-power, water-rat, water-rate, water-ski, water-skiing, water-softener, water-spout, water-supply, water-table,