A narrow notch, groove, or opening, as a keyway in machinery or a slit for a coin in a vending machine. Also: (in sports) a position between the face-off circles on an ice hockey rink, used to kick the ball into the goal. (informal) A place or position, especially one in a group or sequence. Examples may contain sensitive content. These examples have been automatically selected and may not reflect the views of Merriam-Webster or its editors. Send us feedback.

Stacks are symbols that appear in multiple positions on a reel, allowing you to make multiple winning combinations. Stacked symbols are particularly common on penny slot machines, where they can increase your chances of lining up matching symbols on a payline and trigger special game features.

What Is a Slot?

When it comes to aviation, a slot is a period during which an aircraft is authorized by air traffic control to take off or land at a particular airport on a specific day and time. Slots are a crucial tool in managing air traffic at busy airports, as they help to prevent repeated delays caused by too many flights attempting to take off or land at the same time. The use of slots is becoming increasingly common around the world, as busy airports struggle to keep up with the growing demand for air travel. The concept is similar to the use of priority queues at supermarket checkouts. However, the implementation of this type of congestion management has been much more successful, and has resulted in major savings in time and fuel.