The Collaborative International Dictionary of English v.0.48:

Detection \De*tec"tion\, n. [L. detectio an uncovering,
   revealing.]
   The act of detecting; the laying open what was concealed or
   hidden; discovery; as, the detection of a thief; the
   detection of fraud, forgery, or a plot.
   [1913 Webster]

         Such secrets of guilt are never from detection. --D.
                                                  Webster.
   [1913 Webster]

WordNet (r) 3.0 (2006):

detection
    n 1: the perception that something has occurred or some state
         exists; "early detection can often lead to a cure" [syn:
         detection, sensing]
    2: the act of detecting something; catching sight of something
       [syn: detection, catching, espial, spying,
       spotting]
    3: the detection that a signal is being received [syn: signal
       detection, detection]
    4: a police investigation to determine the perpetrator;
       "detection is hard on the feet" [syn: detection,
       detecting, detective work, sleuthing]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "detection":
   amassing evidence, blind flying, blind landing, bringing to light,
   casual discovery, catching, chance discovery, close inquiry,
   department of investigation, detective work, determination,
   determining, disclosure, discovery, distinguishment, espial,
   excavation, exhaustive study, exhumation, exposure, find, finding,
   finding out, hearing, hurricane tracking, indagation, interception,
   invention, investigation, investigative bureau,
   legislative investigation, legwork, locating, location,
   lucky strike, perscrutation, probe, ranging, recognition,
   rediscovery, research, revelation, serendipity, sifting, sleuthing,
   spotting, storm tracking, strike, treasure trove, trouvaille,
   trove, uncovering, unearthing, witch-hunt