someone who shoots at people from a place where they cannot be seen

He was shot and fatally injured by a sniper. 他被一名狙击手击中，身受重伤。

Sniper fire has claimed countless lives these past few weeks. 这几个星期以来，无数人死在狙击手的枪口下。

someone who waits until nearly the end of an auction (= public competition to buy goods) on a website before saying how much money they will offer, in order to be more successful than other people trying to buy the same thing