Source : Webster's Revised Unabridged Dictionary (1913)

Detective \De*tect"ive\, a.
   Fitted for, or skilled in, detecting; employed in detecting
   crime or criminals; as, a detective officer.

Detective \De*tect"ive\, n.
   One who business it is so detect criminals or discover
   matters of secrecy.

Source : WordNet®

detective
     n 1: a police officer who investigates crimes [syn: {investigator},
           {tec}, {police detective}]
     2: an investigator engaged or employed in obtaining information
        not easily available to the public