A liar, swindler, deceiver, angler was someone who was reputable for telling lies.
In 2268, the crew of the USS Enterprise was forced to once again deal with "Harry" Mudd, a con artist that they had had previous dealings with. These dealings ultimately provided an opportunity to confuse an android, Norman, who had been posing as a member of the ship's crew. Describing Mudd to Norman, James T. Kirk stated, "Everything Harry tells you is a lie. Remember that. Everything Harry tells you is a lie." Mudd then told the android, "Listen to this carefully, Norman. I am lying," trapping the android with a type of paradox and eventually leading to a breakdown due to a flood of illogic. (TOS: "I, Mudd")
In reality, this type of paradox is known as the liar paradox.
Garth of Izar once said that Marta was "the greatest liar I have ever met," when she claimed to have written a verse from a play by William Shakespeare. (TOS: "Whom Gods Destroy")
Vash once told Jean-Luc Picard that the problem with being a well-known liar was that nobody believed her even when she told the truth. (TNG: "Qpid")
In 2368, when Helena Rozhenko told Worf that his son Alexander did not always tell the truth, Worf asked if his son was a liar. She replied that he was a boy and boys sometimes took the wrong path. (TNG: "New Ground")
On the planet Brax, Q was known as the "God of Lies". (DS9: "Q-Less")
In 2375, the Doctor created a holographic program of the Cardassian Crell Moset, Medical Consultant Program Beta one. The Doctor wanted him as an expert in exobiology to help him with the case of B'Elanna Torres, who had a cytoplasmic lifeform attached to her. However, Tabor, a Bajoran, recognized Moset as having killed hundreds of people, including members of his own family, having performed experiments on living people. When Moset, unaware of this because of not having been programmed with this knowledge, stated that there must be a mistake, Tabor shouted that he was a liar. (VOY: "Nothing Human")
Agnes Jurati told Jean-Luc Picard that she was a terrible liar, meaning she was not good at lying. (PIC: "The End is the Beginning")