A narrow notch or groove, as in a machine with a slot for coins. (From Webster’s New World College Dictionary, 4th Edition)

If something slots into another item or position, it fits there perfectly. He dropped the coin into the slot and dialed. If a date or time is slotted, it’s reserved or confirmed. Visitors can usually book a slot for a visit a week or more in advance.

In football, a slot receiver is a wide receiver who lines up close to the middle of the field rather than farther out on either side. These players are typically shorter and faster than outside wide receivers, but they need to be able to master every route on the route tree. This includes running precise routes such as slants and quick outs. They also have to block well, since they often line up close to nickel backs or defensive backs on run plays. They must be able to chip blocks on safeties, or crack back blocks on defensive ends. In addition to these responsibilities, Slot receivers must be able to catch passes and run routes just like any other wide receiver. But they are a vital cog in the offensive blocking wheel, and their initial blocking after the snap is especially important. They also need to be aware of which defenders they’re facing, and they must be able to read the defense before the ball is snapped. This is a big part of their job, and it takes a lot of practice to be effective at it.