(covers information from several alternate timelines)
Forgery was the act of creating a false thing. Such a thing was called a fake, a forgery, or a phony.
In 2259 of the alternate reality, Carol Marcus forged her transfer to the USS Enterprise under the alias "Carol Wallace" to determine what was inside the advanced long-range torpedoes, a fact she admitted to James T. Kirk while preparing to open one up. (Star Trek Into Darkness)
In 2293, Spock suggested that if all the torpedoes said to be fired at Kronos One were still present on the USS Enterprise-A, somebody must have forged an entry in the data banks. (Star Trek VI: The Undiscovered Country)
In 2374, Captain Benjamin Sisko and Elim Garak created a forgery of a supposed Dominion meeting outlining a plan to invade Romulus, placed on an optolythic data rod. It was correctly deduced as a fake by Romulan Senator Vreenak, who promised to expose the deception to the entire Alpha Quadrant. However, he was killed by a bomb placed on his shuttle by Garak and carefully staged to make it appear the attack was caused by the Dominion. Furthermore, the rod was discovered in the remains and the imperfections that would have exposed it as a forgery dismissed as damage caused by the explosion. (DS9: "In the Pale Moonlight")