Annul

v. cancel; put an end to

Annulment is a legal procedure for declaring a marriage null and void. Unlike divorce, it is retroactive: an annulled marriage is considered never to have existed.In strict legal terminology, annulment refers only to making a voidable marriage null; if the marriage is void ab initio, then it is automatically null, although a legal declaration of nullity is required to establish this. The process of obtaining such a declaration is similar to the annulment process.
See more at Wikipedia.org...

Verb
1. declare invalid; "The contract was annulled"; "void a plea"
(synonym) invalidate, quash, void, avoid, nullify
(hypernym) cancel, strike down
(hyponym) break
(derivation) annulment, invalidation
2. annul by recalling or rescinding; "He revoked the ban on smoking"; "lift an embargo"; "vacate a death sentence"
(synonym) revoke, lift, countermand, reverse, repeal, overturn, rescind, vacate
(hypernym) cancel, strike down
(hyponym) renege, renege on, renegue on, go back on
(derivation) abrogation, repeal, annulment

(a.)
To reduce to nothing; to obliterate.
  

(a.)
To make void or of no effect; to nullify; to abolish; to do away with; -- used appropriately of laws, decrees, edicts, decisions of courts, or other established rules, permanent usages, and the like, which are made void by component authority.
  

To declare no longer valid