The Collaborative International Dictionary of English v.0.48:

Elastic \E*las"tic\ ([-e]*l[a^]s"t[i^]k), a. [Formed fr. Gr.
   'elay`nein to drive; prob. akin to L. alacer lively, brisk,
   and E. alacrity: cf. F. ['e]lastique.]
   1. Springing back; having a power or inherent property of
      returning to the form from which a substance is bent,
      drawn, pressed, or twisted; springy; having the power of
      rebounding; as, a bow is elastic; the air is elastic;
      India rubber is elastic.
      [1913 Webster]

            Capable of being drawn out by force like a piece of
            elastic gum, and by its own elasticity returning,
            when the force is removed, to its former position.
                                                  --Paley.
      [1913 Webster]

   2. Able to return quickly to a former state or condition,
      after being depressed or overtaxed; having power to
      recover easily from shocks and trials; as, elastic
      spirits; an elastic constitution.
      [1913 Webster]

   Elastic bitumen. (Min.) See Elaterite.

   Elastic curve.
      (a) (Geom.) The curve made by a thin elastic rod fixed
          horizontally at one end and loaded at the other.
      (b) (Mech.) The figure assumed by the longitudinal axis of
          an originally straight bar under any system of bending
          forces. --Rankine.

   Elastic fluids, those which have the property of expanding
      in all directions on the removal of external pressure, as
      the air, steam, and other gases and vapors.

   Elastic limit (Mech.), the limit of distortion, by bending,
      stretching, etc., that a body can undergo and yet return
      to its original form when relieved from stress; also, the
      unit force or stress required to produce this distortion.
      Within the elastic limit the distortion is directly
      proportional to the stress producing it.

   Elastic tissue (Anat.), a variety of connective tissue
      consisting of a network of slender and very elastic fibers
      which are but slightly affected by acids or alkalies.

   Gum elastic, caoutchouc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Elastic \E*las"tic\, n.
   An elastic woven fabric, as a belt, braces or suspenders,
   etc., made in part of India rubber. [Colloq.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

elastic
    adj 1: capable of resuming original shape after stretching or
           compression; springy; "an elastic band"; "a youthful and
           elastic walk" [ant: inelastic]
    2: able to adjust readily to different conditions; "an adaptable
       person"; "a flexible personality"; "an elastic clause in a
       contract" [syn: elastic, flexible, pliable, pliant]
    n 1: a narrow band of elastic rubber used to hold things (such
         as papers) together [syn: rubber band, elastic band,
         elastic]
    2: a fabric made of yarns containing an elastic material

Moby Thesaurus II by Grady Ward, 1.0:

102 Moby Thesaurus words for "elastic":
   Lastex, accommodating, adaptable, adaptive, adjustable, airy,
   animated, baleen, battledore, bendable, bending, bouncy, buoyant,
   chewing gum, compliant, compressible, contractile, convalescent,
   dilatant, distensive, ductile, ebullient, effervescent, elastomer,
   expandable, expansible, expansile, expansional, expansive,
   extensible, extensile, extensional, extensive, fabricable, facile,
   fictile, flexible, flexile, flexuous, formable, formative, gay,
   giving, gum, gum elastic, handball, high-spirited, impressible,
   impressionable, inflatable, inflationary, jumping jack, like putty,
   limber, lissome, lithe, lithesome, lively, malleable, mettlesome,
   moldable, plastic, pliable, pliant, racket, receptive,
   recuperative, recuperatory, resilient, responsive, reviviscent,
   rubber, rubber ball, rubber band, rubberlike, rubbery, sensitive,
   sequacious, shapable, soaring, spandex, spirited, sprightly,
   spring, springboard, springy, stretch, stretch fabric, stretchable,
   stretchy, submissive, supple, susceptible, tractable, tractile,
   trampoline, vivacious, volatile, whalebone, whippy, willowy,
   yielding