When you cut off someone or something, you stop it suddenly or block its path. A driver might cut off another car by pulling in front of it too quickly, forcing the other driver to slam on the brakes. A falling tree branch could cut off the trail you were hiking on, making it impossible to continue forward.

The phrase also means interrupting someone while they're speaking. If you're explaining your science project and your friend starts talking before you finish, they've cut you off. It's considered rude because the person speaking doesn't get to complete their thought.

You can also cut off supplies or resources. A city might have its water cut off during a drought, or parents might cut off a child's allowance as a consequence for bad behavior. In stories, armies sometimes try to cut off their enemy's supply lines to weaken them.

The phrase works literally too: you can cut off a piece of rope, cut off the crust from bread, or use scissors to cut off a loose thread. Whether literal or figurative, cutting something off means bringing something to an abrupt end or creating a sudden separation.