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]

WordNet (r) 3.0 (2006):

gum resin
    n 1: a mixture of resin and gum