To change markedly the appearance or form of: "A thick, fibrous fog had transformed the trees into ghosts and the streetlights into soft, haloed moons\u201d ( David Michael Kaplan). To change the nature, function, or condition of; convert. See Synonyms at convert. Mathematics To subject to a transformation. Electricity To subject to the action of a transformer. Genetics To subject (a cell) to transformation. To undergo a transformation. The result, especially a mathematical quantity or linguistic construction, of a transformation.