1. any substance that lessens the purity or effectiveness of a substance - it is necessary to remove the adulterants before use • Syn: adulterant • Derivationally related forms: adulterate, adulterant (for: adulterant), adulterate (for: adulterant) • Hypernyms: substance 2. a changer who lessens the purity or effectiveness of a substance • Derivationally related forms: adulterate • Hypernyms: changer, modifier