Collins Chinese Dictionary Plus (3rd edition), 2011:
撒手锏(鐧) sāshǒujiǎn 名
trump card
- 不到紧(緊)急关(關)头(頭)不要亮出撒手锏。 Bù dào jǐnjí guāntóu bùyào liàngchū sāshǒujiǎn. Don't reveal your trump card before the crucial moment.