plas·ti·ciz·er noun \ˈplas-tə-ˌs¨©-zər\ Definition of PLASTICIZER : one that plasticizes; specifically : a chemical added especially to rubbers and resins to impart flexibility, workability, or stretchability First Known Use of PLASTICIZER 1925 plas·ti·ciz·er noun (Medical Dictionary) Medical Definition of PLASTICIZER : a chemical added especially to rubbers and resins to impart flexibility, workability, or stretchability