nullification,
override the act of nullifying; making null and void; counteracting or overriding the effect or force of something
neutralisation -
a chemical reaction in which an acid and a base interact with the formation of a salt; with strong acids and bases the essential reaction is the combination of hydrogen ions with hydroxyl ions to form water
chemical reaction,
reaction (chemistry) a process in which one or more substances are changed into others; "there was a chemical reaction of the lime with the ground water"
neutralisation -
(euphemism) the removal of a threat by killing or destroying it (especially in a covert operation or military operation)