The Collaborative International Dictionary of English v.0.48:

Patrolman \Pa*trol"man\, n.; pl. Patrolmen.
   One who patrols; a watchman; especially, a policeman who
   patrols a particular precinct of a town or city.
   [1913 Webster]

WordNet (r) 3.0 (2006):

patrolman
    n 1: a policeman who patrols a given region [syn: flatfoot,
         patrolman]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "patrolman":
   Argus, Charley, G-man, John Law, MP, airplane spotter, bailiff,
   beadle, beagle, bound bailiff, captain, catchpole, chief of police,
   commissioner, constable, cop, deputy, deputy sheriff, detective,
   fed, federal, fire patrolman, fire warden, fireguard, flic,
   forward observer, gendarme, government man, inspector, lictor,
   lieutenant, lookout, lookout man, mace-bearer, marshal,
   mounted policeman, narc, night watchman, officer, patrol,
   patroller, peace officer, picket, police, police captain,
   police commissioner, police constable, police inspector,
   police matron, police officer, police sergeant, policeman,
   policewoman, portreeve, reeve, roundsman, scout, sentinel, sentry,
   sergeant, sergeant at arms, sheriff, spotter, superintendent,
   tipstaff, tipstaves, trooper, vedette, watch, watcher, watchkeeper,
   watchman