the trump card; the finishing move; the winning tactic
Definitions (粵典–words.hk)
名詞
代指一個人最強大嘅武器或者招數,可以攻其不備壓制著對方,以取得勝利;「鐧」本來係一種兵器,「撒手鐧」即係將手上嘅兵器擲向對手,作為奇襲嘅招式 the trump card; the decisive blow; the most powerful gesture