1. 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 Noun
2. (euphemism) the removal of a threat by killing or destroying it (especially in a covert operation or military operation) Noun
3. Action intended to keep a country politically neutral or exclude it from a possible war Noun
4. Action intended to nullify the effects of some previous action Noun