不知所措
Stand at gaze.
To be at loose ends.
To be up a tree.
eg:He was at a loss as to what to do next.
中英俚语俗语来源:三国志·吴志·诸葛恪传:“哀喜交并,不知所措。”
同义词:六神无主 To be all at sea.
反义词:胸有成竹 Have an ace up ones sleeve.