A purge was a complete cleaning or removal of something or someone.
The Vulcan ritual, known as the kolinahr, is designed to purge all remaining emotions in a Vulcan. (ENT: "The Andorian Incident"; Star Trek: The Motion Picture)
Following the demotion of Matthew Ryan to able crewman in 2151, Captain Keene told Jonathan Archer that Ryan would spend the rest of the trip purging hydraulic pumps aboard the ECS Fortunate. (ENT: "Fortunate Son")
Species 8472 threatened to purge the galaxy of all life. (VOY: "In the Flesh")