Capable of being shaped or formed: plastic material such as clay. See Synonyms at malleable. Relating to or dealing with shaping or modeling: the plastic art of sculpture. Having the qualities of sculpture; well-formed: "the astonishing plastic beauty of the chorus girls\u201d ( Frank Harris). Giving form or shape to a substance: the plastic forces that create and wear down a mountain range. Easily influenced; impressionable. Made of a plastic or plastics: a plastic garden hose. Physics Capable of undergoing continuous deformation without rupture or relaxation. Biology Capable of building tissue; formative. Marked by artificiality or superficiality; synthetic: a plastic world of fad, hype, and sensation. Informal Of or obtained by means of credit cards: plastic money. Any of various organic compounds produced by polymerization, capable of being molded, extruded, cast into various shapes and films, or drawn into filaments used as textile fibers. Objects made of plastic. Informal A credit card or credit cards: would accept cash or plastic in payment.