annul
Cross references: 1. nullify an.nul \*-'n*l\ vt or an.nulled; or an.nul.ling [ME annullen, fr. MF annuller, fr. LL annullare, fr. L ad-] + nullus not any - more at NULL 1: to reduce to nothing : OBLITERATE 2: to make ineffective or inoperative : NEUTRALIZE {~ the drug's effect} 3: to declare or make legally void