The Collaborative International Dictionary of English v.0.48:

Gum \Gum\, n. [OE. gomme, gumme, F. gomme, L. gummi and commis,
   fr. Gr. ?, prob. from an Egyptian form kam?; cf. It.
   gomma.]
   1. A vegetable secretion of many trees or plants that hardens
      when it exudes, but is soluble in water; as, gum arabic;
      gum tragacanth; the gum of the cherry tree. Also, with
      less propriety, exudations that are not soluble in water;
      as, gum copal and gum sandarac, which are really resins.
      [1913 Webster]

   2. (Bot.) See Gum tree, below.
      [1913 Webster]

   3. A hive made of a section of a hollow gum tree; hence, any
      roughly made hive; also, a vessel or bin made of a hollow
      log. [Southern U. S.]
      [1913 Webster]

   4. A rubber overshoe. [Local, U. S.]
      [1913 Webster]

   Black gum, Blue gum, British gum, etc. See under
      Black, Blue, etc.

   Gum Acaroidea, the resinous gum of the Australian grass
      tree (Xanlhorrh[oe]a).

   Gum animal (Zool.), the galago of West Africa; -- so called
      because it feeds on gums. See Galago.

   Gum animi or anim['e]. See Anim['e].

   Gum arabic, a gum yielded mostly by several species of
      Acacia (chiefly A. vera and A. Arabica) growing in
      Africa and Southern Asia; -- called also gum acacia.
      East Indian gum arabic comes from a tree of the Orange
      family which bears the elephant apple.

   Gum butea, a gum yielded by the Indian plants Butea
      frondosa and B. superba, and used locally in tanning
      and in precipitating indigo.

   Gum cistus, a plant of the genus Cistus (Cistus
      ladaniferus), a species of rock rose.

   Gum dragon. See Tragacanth.

   Gum elastic, Elastic gum. See Caoutchouc.

   Gum elemi. See Elemi.

   Gum juniper. See Sandarac.

   Gum kino. See under Kino.

   Gum lac. See Lac.

   Gum Ladanum, a fragrant gum yielded by several Oriental
      species of Cistus or rock rose.

   Gum passages, sap receptacles extending through the
      parenchyma of certain plants (Amygdalace[ae],
      Cactace[ae], etc.), and affording passage for gum.

   Gum pot, a varnish maker's utensil for melting gum and
      mixing other ingredients.

   Gum resin, the milky juice of a plant solidified by
      exposure to air; one of certain inspissated saps, mixtures
      of, or having properties of, gum and resin; a resin
      containing more or less mucilaginous and gummy matter.

   Gum sandarac. See Sandarac.

   Gum Senegal, a gum similar to gum arabic, yielded by trees
      (Acacia Verek and A. Adansoni[aum]) growing in the
      Senegal country, West Africa.

   Gum tragacanth. See Tragacanth.

   Gum water, a solution of gum, esp. of gum arabic, in water.


   Gum wood, the wood of any gum tree, esp. the wood of the
      Eucalyptus piperita, of New South Wales.
      [1913 Webster]

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.
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   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:

Caoutchouc \Caout"chouc\, n. [F. caoutchouc, from the South
   American name.]
   A tenacious, elastic, gummy substance obtained from the milky
   sap of several plants of tropical South America (esp. the
   euphorbiaceous tree Siphonia elastica or Hevea
   caoutchouc), Asia, and Africa. Being impermeable to liquids
   and gases, and not readly affected by exposure to air, acids,
   and alkalies, it is used, especially when vulcanized, for
   many purposes in the arts and in manufactures. Also called
   India rubber (because it was first brought from India, and
   was formerly used chiefly for erasing pencil marks) and gum
   elastic. See Vulcanization.
   [1913 Webster]

   Mineral caoutchouc. See under Mineral.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gum elastic
    n 1: an elastic material obtained from the latex sap of trees
         (especially trees of the genera Hevea and Ficus) that can
         be vulcanized and finished into a variety of products [syn:
         rubber, natural rubber, India rubber, gum elastic,
         caoutchouc]