The definition of annul means to do away with, make null and void or reduce to nothing.
(verb)An example of annul is to invalidate a marriage.
See annul in Webster's New World College Dictionary
See annul in American Heritage Dictionary 4
transitive verb an·nulled, an·nul·ling, an·nuls
Origin:
Origin: Middle English annullen
Origin: , from Old French annuller
Origin: , from Late Latin annullāre
Origin: : Latin ad-, ad-
Origin: + Latin nullus, none; see ne in Indo-European roots
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