Expunging was the act of purging an offender's criminal record. It was often accompanied by a pardon. (DIS: "Will You Take My Hand?")
In 2257, Michael Burnham's criminal record for mutiny was expunged, allowing her to serve in Starfleet once again. (DIS: "Will You Take My Hand?")
In 2372, during Quinn's hearing regarding his right to commit suicide, when asked by Tuvok about his own previous discipline by the Q Continuum, Q explained that his record had been expunged. (VOY: "Death Wish")