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.
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   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.]
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   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:

Blue \Blue\ (bl[=u]), a. [Compar. Bluer (bl[=u]"[~e]r);
   superl. Bluest.] [OE. bla, blo, blew, blue, livid, black,
   fr. Icel.bl[=a]r livid; akin to Dan. blaa blue, Sw. bl[*a],
   D. blauw, OHG. bl[=a]o, G. blau; but influenced in form by F.
   bleu, from OHG. bl[=a]o.]
   1. Having the color of the clear sky, or a hue resembling it,
      whether lighter or darker; as, the deep, blue sea; as blue
      as a sapphire; blue violets. "The blue firmament."
      --Milton.
      [1913 Webster]

   2. Pale, without redness or glare, -- said of a flame; hence,
      of the color of burning brimstone, betokening the presence
      of ghosts or devils; as, the candle burns blue; the air
      was blue with oaths.
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   3. Low in spirits; melancholy; as, to feel blue.
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   4. Suited to produce low spirits; gloomy in prospect; as,
      thongs looked blue. [Colloq.]
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   5. Severe or over strict in morals; gloom; as, blue and sour
      religionists; suiting one who is over strict in morals;
      inculcating an impracticable, severe, or gloomy mortality;
      as, blue laws.
      [1913 Webster]

   6. Literary; -- applied to women; -- an abbreviation of
      bluestocking. [Colloq.]
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            The ladies were very blue and well informed.
                                                  --Thackeray.
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   Blue asbestus. See Crocidolite.

   Blue black, of, or having, a very dark blue color, almost
      black.

   Blue blood. See under Blood.

   Blue buck (Zool.), a small South African antelope
      (Cephalophus pygm[ae]us); also applied to a larger
      species ([AE]goceras leucoph[ae]us); the blaubok.

   Blue cod (Zool.), the buffalo cod.

   Blue crab (Zool.), the common edible crab of the Atlantic
      coast of the United States (Callinectes hastatus).

   Blue curls (Bot.), a common plant (Trichostema
      dichotomum), resembling pennyroyal, and hence called also
      bastard pennyroyal.

   Blue devils, apparitions supposed to be seen by persons
      suffering with delirium tremens; hence, very low
      spirits. "Can Gumbo shut the hall door upon blue devils,
      or lay them all in a red sea of claret?" --Thackeray.

   Blue gage. See under Gage, a plum.

   Blue gum, an Australian myrtaceous tree (Eucalyptus
      globulus), of the loftiest proportions, now cultivated in
      tropical and warm temperate regions for its timber, and as
      a protection against malaria. The essential oil is
      beginning to be used in medicine. The timber is very
      useful. See Eucalyptus.

   Blue jack, Blue stone, blue vitriol; sulphate of copper.


   Blue jacket, a man-of war's man; a sailor wearing a naval
      uniform.

   Blue jaundice. See under Jaundice.

   Blue laws, a name first used in the eighteenth century to
      describe certain supposititious laws of extreme rigor
      reported to have been enacted in New Haven; hence, any
      puritanical laws. [U. S.]

   Blue light, a composition which burns with a brilliant blue
      flame; -- used in pyrotechnics and as a night signal at
      sea, and in military operations.

   Blue mantle (Her.), one of the four pursuivants of the
      English college of arms; -- so called from the color of
      his official robes.

   Blue mass, a preparation of mercury from which is formed
      the blue pill. --McElrath.

   Blue mold or Blue mould, the blue fungus (Aspergillus
      glaucus) which grows on cheese. --Brande & C.

   Blue Monday,
      (a) a Monday following a Sunday of dissipation, or itself
          given to dissipation (as the Monday before Lent).
      (b) a Monday considered as depressing because it is a
          workday in contrast to the relaxation of the weekend.


   Blue ointment (Med.), mercurial ointment.

   Blue Peter (British Marine), a blue flag with a white
      square in the center, used as a signal for sailing, to
      recall boats, etc. It is a corruption of blue repeater,
      one of the British signal flags.

   Blue pill. (Med.)
      (a) A pill of prepared mercury, used as an aperient, etc.
      (b) Blue mass.

   Blue ribbon.
      (a) The ribbon worn by members of the order of the Garter;
          -- hence, a member of that order.
      (b) Anything the attainment of which is an object of great
          ambition; a distinction; a prize. "These
          [scholarships] were the --blue ribbon of the college."
          --Farrar.
      (c) The distinctive badge of certain temperance or total
          abstinence organizations, as of the --Blue ribbon
          Army.

   Blue ruin, utter ruin; also, gin. [Eng. Slang] --Carlyle.

   Blue spar (Min.), azure spar; lazulite. See Lazulite.

   Blue thrush (Zool.), a European and Asiatic thrush
      (Petrocossyphus cyaneas).

   Blue verditer. See Verditer.

   Blue vitriol (Chem.), sulphate of copper, a violet blue
      crystallized salt, used in electric batteries, calico
      printing, etc.

   Blue water, the open ocean.

   Big Blue, the International Business Machines corporation.
      [Wall Street slang.] PJC

   To look blue, to look disheartened or dejected.

   True blue, genuine and thorough; not modified, nor mixed;
      not spurious; specifically, of uncompromising
      Presbyterianism, blue being the color adopted by the
      Covenanters.
      [1913 Webster]

            For his religion . . .
            'T was Presbyterian, true blue.       --Hudibras.
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WordNet (r) 3.0 (2006):

blue gum
    n 1: tall fast-growing timber tree with leaves containing a
         medicinal oil; young leaves are bluish [syn: blue gum,
         fever tree, Eucalyptus globulus]