Other forms: patrolmen
A patrolman is another name for a police officer. Most patrolmen keep an eye on a certain area while walking or driving around it.
The word patrolman is a bit old fashioned, since it's really only appropriate for a man — you can call a female officer a "patrolwoman," but it's simpler to just call them both police officers. Patrolman was first used in the 1840s to distinguish British constables who walked a beat, patrolling a specific neighborhood or region on foot. Patrol comes from the French patrouille, "a night watch."