Someone who practices Legilimency is known as a Legilimens. A skilled Legilimens would be easily able to detect truth or deception and would also be able to tell what a person was thinking or remembering.
In Harry Potter and the Order of the Phoenix, former Death Eater and Hogwarts Potions Master Severus Snape uses his talent in Legilimency to teach student Harry Potter to stop mental intrusion by Lord Voldemort. It has also been hinted that Voldemort excels at Legilimency, as he has on several occasions been able to determine with unerring accuracy whether people are lying.
This nonexistent word was created by joining forms of the Latin words Legens (reader) and Mens (mind) with "-mancy" (which means divination).