WordNet (r) 3.0 (2006):

rubbery
    adj 1: having an elastic texture resembling rubber in
           flexibility or toughness [syn: rubbery, rubberlike]
    2: difficult to chew [syn: cartilaginous, gristly,
       rubbery]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "rubbery":
   able to adapt, adaptable, adjustable, alterable, alterative,
   anemic, asthenic, bloodless, changeable, checkered, chicken,
   cowardly, debilitated, drooping, droopy, dull, effete, etiolated,
   ever-changing, faint, faintish, feeble, flabby, flaccid, flexible,
   flimsy, floppy, fluid, gone, gutless, imbecile, impermanent,
   impotent, kaleidoscopic, languid, languorous, lax, limber, limp,
   listless, loose, lustless, malleable, many-sided, marrowless,
   metamorphic, mobile, modifiable, movable, mutable, nerveless,
   nonuniform, permutable, pithless, plastic, pooped, powerless,
   protean, proteiform, relaxed, resilient, rubber, rubberized,
   rubberlike, sapless, sinewless, slack, soft, spineless,
   strengthless, supple, transient, transitory, unhardened, unnerved,
   unstrung, variable, weak, weakly