The Collaborative International Dictionary of English v.0.48:

Nonelastic \Non`e*las"tic\, a.
   Not having elasticity; not able to be stretched reversibly.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "nonelastic":
   adamant, adamantine, immovable, immutable, inductile, inelastic,
   inextensible, inextensile, inextensional, inflexible, intractable,
   intractile, irresilient, nonstretchable, stubborn, unalterable,
   unbending, unextendible, unextensible, unflexible, ungiving,
   unlimber, unmalleable, unpliable, unpliant, untractable,
   unyielding