Abrogation is the act of canceling, nullifying, or repealing something, almost always in an official or legal context.
To abrogate something is to repeal or cancel it, so abrogation is the act of repealing or canceling. This is mainly a legal term. Abrogation occurs whenever an old law or rule is abolished, like when slavery was outlawed. The abrogation of a lease means it is no longer valid and binding. The annulment of a marriage — which legally wipes out the marriage, as if it never happened — is also a type of abrogation.