(n.) One who nullifies or makes void; one who maintains the right to nullify a contract by one of the parties.

acid acidity agent alexipharmic alkali alkalinity alkalizer alloisomer anion annulling anthelmintic antibiotic antidotal antidote antimicrobial antipyretic antitoxic atom bacteriostatic base bicarbonate of soda biochemical buffer buffering calcium carbonate canceling cation chemical chemical element chromoisomer compound copolymer counteractant counteractive counteragent counterbalancing counterirritant dimer element febrifugal gastric antacid heavy chemicals high polymer homopolymer hydracid inorganic chemical ion isomer macromolecule magnesia metamer molecule monomer negating neutralizer neutralizing nonacid nullifier nullifying offset offsetting organic chemical oxyacid polymer preventative preventive prophylactic pseudoisomer radical reagent remedy seltzer sodium bicarbonate stultifying sulfacid trimer vitiating voiding