get / take / have the measure of sb
摸清某人的底細
to form an opinion about sb's character or abilities so that you can deal with them
After only one game, the chess champion had the measure of his young opponent.僅僅一局過後,這位國際象棋冠軍就摸清了年輕對手的實力。
釋義來自《牛津高階英漢雙解詞典》第 9 版