A deception was an act or statement which concealed or distorted the truth. It was also known as a ruse, subterfuge, or deceit.
In 2266, after learning that commander Balok tested the crew of the USS Enterprise to discover their real intentions, Captain James T. Kirk protested that the memory banks of his ship had been probed. To which, Balok responded that the records might be a deception on the part of the Humans. (TOS: "The Corbomite Maneuver")