项xiàng庄zhuāng舞wǔ剑jiàn

Literal: Xiang Zhuang dances with his sword
Figurative: To do something seemingly harmless that actually masks a hostile intent aimed at someone else; an act with an ulterior motive. Often completed with the phrase meaning "the real target is somebody else."

Where does 项庄舞剑 come from?

At the Feast at Hongmen, the warlord Xiang Yu hosted his rival Liu Bang, the future founder of the Han dynasty. The strategist Fan Zeng wanted to use the banquet to kill Liu Bang, so he had Xiang Zhuang perform a sword dance as entertainment, planning to edge close to Liu Bang and run him through "by accident." Xiang Bo, Xiang Yu's uncle, saw through the ploy and rose to dance as well, shielding Liu Bang with his own body. Recognizing the danger, the adviser Zhang Liang uttered the famous line: "Xiang Zhuang dances with his sword, but his aim is on Pei Gong (Liu Bang)." Forewarned, Liu Bang managed to escape alive.

Source (出处): 《史记·项羽本纪》

How is 项庄舞剑 used? Two examples

他tā请qǐng你nǐ吃chī饭fàn还hái送sòng礼lǐ物wù，其qí实shí是shì项xiàng庄zhuāng舞wǔ剑jiàn，想xiǎng让ràng你nǐ帮bāng他tā签qiān那nà份fèn合hé同tóng。
He treats you to dinner and even brings a gift, but there's an ulterior motive: he wants you to sign that contract for him.
她tā表biǎo面miàn上shàng是shì在zài夸kuā新xīn同tóng事shì，可kě这zhè番fān话huà项xiàng庄zhuāng舞wǔ剑jiàn，明míng摆bǎi着zhe是shì说shuō给gěi经jīng理lǐ听tīng的de。
On the surface she's praising the new colleague, but the remark has a hidden aim: she's obviously saying it for the manager to hear.

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