A deception was an act or statement which concealed or distorted the truth. It was also known as a ruse, subterfuge, or deceit.
In 2254, after Lieutenant Una Chin-Riley stated that it was wrong to create a race of Human slaves, the Talosian Magistrate asked if this was a deception. (TOS: "The Cage")
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")
According to a Romulan commander in 2268, it was unworthy of a Vulcan to resort to subterfuge. (TOS: "The Enterprise Incident")