Synonyms for Annulment (same or very similar meaning)
WordNet sense 1 (the state of being cancelled or annulled):
revocationWordNet sense 2 ((law) a formal termination (of a relationship or a judicial proceeding etc)):
invalidationWordNet sense 3 (the act of abrogating; an official or legal cancellation):
abrogation, repealFrom the ODE community, based on WordNetadd/edit