Patrol means to move regularly through an area to watch for problems, keep things safe, or make sure everything is running smoothly. Police officers patrol neighborhoods, walking or driving through streets to deter crime and respond quickly if something goes wrong. Security guards patrol buildings, checking doors and watching for anything unusual.

The word comes from military practice, where soldiers patrol borders or territories to spot potential threats. On a patrol, they follow a route through their assigned area, staying alert for anything that seems out of place.

Schools might have teachers who patrol hallways between classes, making sure students get where they need to go safely. Park rangers patrol wilderness areas to help lost hikers and protect wildlife. Lifeguards patrol beaches, scanning the water for swimmers in trouble.

You can use patrol as a noun too: “The police sent out extra patrols during the festival” means they sent extra officers to watch over the event. A patrol is both the act of patrolling and the group doing it, like when a military patrol heads out on a mission.

The key idea is regular, watchful movement through a space. Someone on patrol isn't just passing through once; they're making repeated rounds, keeping an eye on things, ready to spot and handle whatever comes up.