The Collaborative International Dictionary of English v.0.48:

nonresilient \nonresilient\ adj.
   Not rebounding with the normal or expected velocity.
   [Narrower terms: inelastic (vs. elastic)]

   Syn: dead.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nonresilient
    adj 1: not resilient