a plan or piece of information kept secret until it becomes necessary to use it
手中握有王牌；有应急妙计
have all the advantages
占尽优势
use one's best resource
打出王牌；使出绝招
deciding to play her ace, Emily showed the letter to Vic.
艾米丽决定使出杀手锏，把信拿给维克看。
On the verge of; very near to
差一点，几乎；非常接近
came within an ace of losing the election.
几乎失去竞选
A hidden advantage or resource kept in reserve until needed.
锦囊妙计：隐藏的优势或资源，一直保存到需要时