A person who alters or fabricates information, documents, or evidence with the intent to deceive. The police arrested the falsifier for creating fake passports.
An object, device, or mechanism that falsifies data or produces falsified output. Engineers fed the signals through a falsifier to simulate faulty sensor readings.
Logic, model theory: a structure or interpretation in which a given statement or formula is false. A non-standard model can serve as a falsifier for certain arithmetic propositions.