Apostatised means that a person has deliberately abandoned or renounced a belief, faith, or allegiance they once strongly held, most often in a religious context. When someone is described as having apostatised, it implies a conscious decision to turn away from their previous convictions, sometimes in favor of new beliefs or simply a rejection of the old ones. The term often carries a sense of seriousness or finality, as it suggests not just doubt or questioning, but a clear break from a prior identity or commitment.