Ace in the Hole (Cole Porter song) definition

Ace in the Hole (Cole Porter song)

WiktionaryText

From stud poker in which there is one unknown card called the "hole card;" referring to the optimum "hole card" being an ace.

A hidden or secret strength, or unrevealed advantage.

Our ace in the hole left our opponents stupefied; it isn't every day that an NBA star plays street basketball.