To bump means to hit or knock against something, usually by accident and without much force. You might bump your knee on a table corner while walking through a dark room, or bump into a friend you didn't expect to see at the store.

When cars bump each other in a parking lot, they make contact gently, unlike a serious crash. A small raised area on a surface is also called a bump, like the bump on your head after you've hit it, or the speed bumps in parking lots that make drivers slow down.

The word suggests something sudden but not too serious. When a plane hits turbulence, passengers might feel a bump as the aircraft moves through rough air. In everyday conversation, people use bump to describe minor collisions and disruptions: a toddler bumps into furniture while learning to walk, or you might bump your elbow against a doorframe while carrying a big box.

You can also bump someone up in line, meaning you move them to a better position, or bump up the volume on your speakers, meaning you increase it. These uses share the idea of a small, sudden change.