yǐzǐzhīmáogōngzǐzhīdùn
to use someone's own weapon against them
以子之矛，攻子之盾 yǐzǐzhīmáogōngzǐzhīdùn
- to use someone's own weapon against them
- To attack an opponent using their own arguments, theories, or methods; literally "use your spear to attack your shield."