ace

have an ace up your sleeve have an effective resource or piece of information kept hidden until it is necessary to use it; have a secret advantage.

☞ The ace is the highest playing card in its suit in many card games, so a cheating player might well hide one to use against an unwary opponent. A North American variant is an ace in the hole. The next two idioms are also based on this meaning of ace.

hold all the aces have all the advantages.

play your ace use your best resource.

within an ace of very close to.

☞ Ace here has the figurative meaning of 'a tiny amount' and is used with reference to the single spot on the playing card. The phrase was first recorded in the early 18th century.