Select the most appropriate meaning of the given idiom.

Ace in the hole

The correct answer is: A major advantage that one keeps hidden until an ideal time.

Key Points

• "Ace in the hole" is an idiomatic expression that originated from poker, specifically stud poker. In stud poker, each player receives some cards face-up and others face-down. The face-down cards are called "hole cards." The "ace" is the highest-ranking card in many card games.
• The idiom "Ace in the hole" figuratively refers to a hidden advantage or resource that a person keeps secret until the right moment.
• It represents a powerful tool or strategy that can be revealed when needed to gain a significant advantage over others. This advantage is typically withheld or kept in reserve until an opportune time arises, maximizing its impact and effectiveness.

Therefore, the correct meaning of the idiom "Ace in the hole" is: A major advantage that one keeps hidden until an ideal time.