A mousetrap is a device designed to catch mice. The most common type has a wooden base with a spring-loaded metal bar that snaps down when a mouse touches the bait (usually cheese or peanut butter). When the mouse goes for the food, snap! The bar comes down and traps it.

People use mousetraps because mice can damage homes by chewing through wires, walls, and food packages. While the classic snap trap has been around since the 1890s, today there are many kinds: some catch mice alive in small cages so they can be released outside, while others use glue or electronic sensors.

The word mousetrap also appears in the expression “build a better mousetrap,” which means to improve an existing invention or find a cleverer solution to a common problem. If you figure out a faster way to organize your locker or a more efficient method for finishing homework, you've built your own “better mousetrap.”

Interestingly, The Mousetrap is also the name of a famous mystery play by Agatha Christie that has been running in London since 1952, making it the longest-running play in history. The title refers to a trap set to catch a criminal, just like the device catches a mouse.