To harass someone means to bother them repeatedly in a way that makes them uncomfortable, upset, or unable to do what they need to do. When someone harasses another person, they might tease them relentlessly even after being asked to stop, follow them around when they want to be left alone, or keep pestering them with unwanted attention.

Harassment goes beyond ordinary annoyance. If your brother asks you one question while you're doing homework, that's just annoying. But if he keeps interrupting you over and over, making it impossible to concentrate even after you've asked him to stop, he's harassing you. The key difference is the persistence and the refusal to respect someone's boundaries.

At school, harassment might look like a student constantly making mean comments about someone's appearance, or repeatedly excluding someone from activities on purpose. In the animal world, smaller birds sometimes harass larger predators like hawks by diving at them repeatedly to drive them away from their nests.

The related noun is harassment. Laws against harassment exist to help protect people's safety and rights. If someone experiences harassment, they can tell a trusted adult who can help make it stop.