WordNet (r) 3.0 (2006):

stakeout
    n 1: surveillance of some place or some person by the police (as
         in anticipation of a crime)

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "stakeout":
   bugging, cloak-and-dagger work, counterespionage,
   counterintelligence, electronic surveillance, espial, espionage,
   following, intelligence, intelligence work, military intelligence,
   observation, secret police, secret service, shadowing, spying,
   surveillance, tailing, trailing, wiretap, wiretapping