“plastic… I. a. Having the power of molding or shaping formless or yielding material (as, “that divine plastic force which is for ever molding human society”: Mrs. H. Ward’s “Robert Elsmere,” xxxii.) concerned with or pertaining to molding or modeling (as, plastic arts, such as sculpture and ceramics); produced by molding (as, plastic figures); also, capable of being molded or of receiving form (as, plastic substances, such as clay, wax, or plaster); fif., capable of being brought to a definite condition or character (as, “The world is plastic for men to do what they will with it,” H. G. Wells’s “Mr. Britling,” ii. 1~6; the plastic mind of youth); pliable; impressionable; in surg., concerned with or pertaining to the remedying or restoring of malformed, injured, or lost parts (as, plastic surgery; a plastic operation); in biol. and pathol., concerned with or pertaining to the formation of new tissue in the living body. II. n. A plastic substance. ... The quality or property of being plastic; esp., capability of being molded, receiving shape, or being brought to a definite form or character.”
-from The New Century Dictionary, 1944 ed.