The Collaborative International Dictionary of English v.0.48:

Elasticity \E`las*tic"i*ty\ ([=e]`l[a^]s*t[i^]s"[i^]*t[y^]), n.
   [Cf. F. ['e]lasticit['e].]
   1. The quality of being elastic; the inherent property in
      bodies by which they recover their former figure or
      dimensions, after the removal of external pressure or
      altering force; springiness; resilience; tendency to
      rebound; as, the elasticity of caoutchouc; the elasticity
      of the air.
      [1913 Webster]

   2. Power of resistance to, or recovery from, depression or
      overwork; -- usually referred to as resilience[3].
      [1913 Webster]

   Coefficient of elasticity, the quotient of a stress (of a
      given kind), by the strain (of a given kind) which it
      produces; -- called also coefficient of resistance.

   Surface of elasticity (Geom.), the pedal surface of an
      ellipsoid (see Pedal); a surface used in explaining the
      phenomena of double refraction and their relation to the
      elastic force of the luminous ether in crystalline media.
      [1913 Webster]

WordNet (r) 3.0 (2006):

elasticity
    n 1: the tendency of a body to return to its original shape
         after it has been stretched or compressed; "the waistband
         had lost its snap" [syn: elasticity, snap] [ant:
         inelasticity]

Moby Thesaurus II by Grady Ward, 1.0:

63 Moby Thesaurus words for "elasticity":
   adaptability, adjustability, agreeability, amenability, beef,
   beefiness, bendability, brawn, brawniness, ductibility, ductility,
   extendibility, extensibility, facility, fictility, flexibility,
   flexility, flexuousness, formativeness, give, heftiness, huskiness,
   impressionability, involuntary muscle, limberness, litheness,
   malleability, moldability, muscle, muscularity, musculature,
   physique, plasticity, pliability, pliancy, receptiveness,
   resilience, responsiveness, rubberiness, sensibility,
   sensitiveness, sequacity, sinew, sinewiness, sinews, springiness,
   stretch, stretchability, stretchiness, submissiveness, suppleness,
   susceptibility, tensileness, tensility, thew, thewiness, thews,
   tolerance, tone, tractability, tractility, voluntary muscle,
   willowiness