Surveillance

from WordNet (r) 3.0 (2006)

surveillance
    n 1: close observation of a person or group (usually by the
         police)

from The Collaborative International Dictionary of English v.0.48

Surveillance \Sur*veil"lance\, n. [F., fr. surveiller to watch
   over; sur over + veiller to watch, L. vigilare. See {Sur-},
   and {Vigil}.]
   Oversight; watch; inspection; supervision.
   [1913 Webster]

         That sort of surveillance of which . . . the young have
         accused the old.                         --Sir W.
                                                  Scott.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

70 Moby Thesaurus words for "surveillance":
      accountability, ambuscade, ambush, ambushment, auspices, blind,
      booby trap, bossing, bugging, care, charge, cloak-and-dagger work,
      counterespionage, counterintelligence, custodianship, custody,
      eagle eye, electronic surveillance, espial, espionage, eye,
      following, guard, guardedness, guardianship, intelligence,
      intelligence work, intendance, invigilation, jurisdiction, lookout,
      lurking hole, military intelligence, monitoring, observance,
      observation, oversight, peeled eye, proctoring, prudence, qui vive,
      reconnaissance, responsibility, scrutiny, secret police,
      secret service, shadowing, sharp eye, spying, stakeout,
      stalking-horse, stewardship, superintendence, supervision, tab,
      tailing, tout, trailing, trap, vigil, vigilance, wariness, watch,
      watch and ward, watchful eye, watchfulness, watching, weather eye,
      wiretap, wiretapping