Caout·chouc n.  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.
 Mineral caoutchouc. See under Mineral.
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 E·las·tic a.
 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.
    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.
 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.
 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.
 Gum, n.
 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.
 2. Bot. See Gum tree, below.
 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.]
 4. A rubber overshoe. [Local, U. S.]
 Black gum, Blue gum, British gum, etc. See under Black, Blue, etc.
 Gum Acaroidea, the resinous gum of the Australian grass tree (Xanlhorrhœa).
 Gum animal Zool., the galago of West Africa; -- so called because it feeds on gums. See Galago.
 Gum animi or animé. See Animé.
 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 (Amygdalaceæ, Cactaceæ, 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. Adansoniä) 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.
 gum elastic
      n : latex from trees (especially trees of the genera Hevea and
          Ficus) [syn: rubber, India rubber, caoutchouc]