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]