A narrow opening for receiving or admitting something, such as a coin or letter. Also called hole, slot, slit, or aperture. The term is most often applied to the interior opening of a postal box, into which letters and postcards are dropped. But it can also refer to an airport slot, which gives a specific airline the right to operate at a congested airport at particular times.

When electromechanical slot machines were first introduced, they were vulnerable to a variety of cheating techniques. For example, some were equipped with “tilt switches” that would make or break a circuit if the machine was tilted, thereby making it appear that a certain symbol had a high probability of appearing on the payline. But with the advent of microprocessors in modern slot machines, it became possible to give each symbol a different probability of being displayed on a given reel. This allowed the manufacturers to maintain a consistent appearance of symbols on all the reels while still providing the player with the illusion that some symbols were closer to winning than others.

In ice hockey, the slot is the area directly in front of the net that offers the best chance for a center or winger to score without a deflection. When a player is in the low slot, it is important that he or she keep the puck away from the defensive zone. Similarly, when an aircraft is in the slot of an air traffic control system, it should remain there until an opening is available. This approach can reduce delays and fuel burn.