Argus, Charley, airplane spotter, beat, course, cover, defend, defending, do, fire patrolman, fire warden, fireguard, forward observer, go over, guard, guarding, keep guard, keep vigil, keep watch, lookout, lookout man, measure, mount guard, night watchman, overpass, pass over, pass through, patroller, patrolman, perambulate, peregrinate, pererrate, picket, ply, police, protect, protecting, protection, range, range over, reconnoiter, rounds, roundsman, safeguarding, scour, scour the country, scout, sentinel, sentry, spotter, stand guard, stand sentinel, sweep, track, transit, travel over, travel through, traverse, vedette, vigilance, voyage, watch, watch over, watcher, watchfulness, watchkeeper, watchman