In psychology, projection was a defense mechanism in which a person refused to acknowledge certain emotions, thoughts, or feelings in themselves and attributed or applied them to others instead. Doctor Sigmund Freud invented the idea of projection in the 19th century.
In 2377, Deanna Troi suggesting that Reginald Barclay was projecting his suspicions of his ex-girlfriend Leosa onto others after his hologram for the Pathfinder Project disappeared. (VOY: "Inside Man")
In 3189, Acting Captain Sylvia Tilly accused Osyraa, leader of the Emerald Chain, of projecting her feeling of being a fraud onto her. (DIS: "Su'Kal")