a. - Capable of being molded, formed, or modeled, as clay or plaster; -- used also figuratively; as, the plastic mind of a child.
a. - Pertaining or appropriate to, or characteristic of, molding or modeling; produced by, or appearing as if produced by, molding or modeling; -- said of sculpture and the kindred arts, in distinction from painting and the graphic arts.
n. - a substance composed predominantly of a synthetic organic high polymer capable of being cast or molded; many varieties of plastic are used to produce articles of commerce (after 1900). [MW10 gives origin of word as 1905]