an·nul 
(ə-nŭl)
(ə-nŭl)tr.v. an·nulled, an·nul·ling, an·nuls
1. To make or declare void or invalid, as a marriage or a law; nullify.
2. To bring to an end the effect or existence of; cancel out: "That task would be easier to perform now that his personal stake in it was annulled" (Edith Wharton).
[Middle English annullen, from Old French annuller, from Late Latin annullāre : Latin ad-, ad- + Latin nullus, none; see ne in the Appendix of Indo-European roots.]