俟[竢]sì

 [书] （等待） wait: ～ 机进攻 wait for an opportunity to attack; 一 ～ 准备就绪， 即行公开展出。 The exhibition will be opened as soon as everything is in order.
另见 see also qí。
◆俟河之清 wait till the Yellow River runs clear water; once in a blue moon; wait for the millennium；
俟机 wait for an opportunity; watch for one's chance