The Collaborative International Dictionary of English v.0.48:

resilience \re*sil"i*ence\ (r[-e]*z[i^]l"[i^]*ens), resiliency
\re*sil"i*en*cy\ (r[-e]*z[i^]l"[i^]*en*s[y^]), n.
   1. The act of springing back, rebounding, or resiling; as,
      the resilience of a ball or of sound.
      [1913 Webster]

   2. The power or inherent property of returning to the form
      from which a substance is bent, stretched, compressed, or
      twisted; elasticity[1]; springiness; -- of objects and
      substances.
      [PJC]

   3. Hence: The power or ability to recover quickly from a
      setback, depression, illness, overwork or other adversity;
      buoyancy; elasticity[2]; -- of people.
      [PJC]

   4. (Mech. & Engin.) The mechanical work required to strain an
      elastic body, as a deflected beam, stretched spring, etc.,
      to the elastic limit; also, the work performed by the body
      in recovering from such strain.
      [1913 Webster]

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):

resilience
    n 1: the physical property of a material that can return to its
         original shape or position after deformation that does not
         exceed its elastic limit [syn: resilience, resiliency]
    2: an occurrence of rebounding or springing back [syn:
       resilience, resiliency]

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "resilience":
   adaptability, adjustability, airiness, alterability, backfire,
   backlash, backlashing, boomerang, bounce, bounciness, bound,
   breeziness, buoyance, buoyancy, carefreeness, carom, changeability,
   changeableness, changefulness, chirpiness, contrecoup,
   debonairness, elasticity, extensibility, flexibility, fluidity,
   give, impermanence, jauntiness, kick, kickback, levity,
   light heart, lightheartedness, lightness, lightsomeness,
   liveliness, malleability, mobility, modifiability, movability,
   mutability, nonuniformity, perkiness, permutability, pertness,
   plasticity, rebound, rebuff, recalcitration, recoil, repercussion,
   repulse, resiliency, responsiveness, ricochet, rubberiness, snap,
   spring, springiness, stretch, stretchability, stretchiness,
   suppleness, tone, tonicity, tonus, transience, transitoriness