The Collaborative International Dictionary of English v.0.48:

Bubble \Bub"ble\, n. [Cf. D. bobbel, Dan. boble, Sw. bubbla. Cf.
   Blob, n.]
   1. A thin film of liquid inflated with air or gas; as, a soap
      bubble; bubbles on the surface of a river.
      [1913 Webster]

            Beads of sweat have stood upon thy brow,
            Like bubbles in a late disturbed stream. --Shak.
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   2. A small quantity of air or gas within a liquid body; as,
      bubbles rising in champagne or a["e]rated waters.
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   3. A globule of air, or globular vacuum, in a transparent
      solid; as, bubbles in window glass, or in a lens.
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   4. A small, hollow, floating bead or globe, formerly used for
      testing the strength of spirits.
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   5. The globule of air in the spirit tube of a level.
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   6. Anything that wants firmness or solidity; that which is
      more specious than real; a false show; a cheat or fraud; a
      delusive scheme; an empty project; a dishonest
      speculation; as, the South Sea bubble.
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            Then a soldier . . .
            Seeking the bubble reputation
            Even in the cannon's mouth.           --Shak.
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   7. A person deceived by an empty project; a gull. [Obs.]
      "Ganny's a cheat, and I'm a bubble." --Prior.
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The Collaborative International Dictionary of English v.0.48:

Bubble \Bub"ble\, v. i. [imp. & p. p. Bubbled; p. pr. & vb. n.
   Bubbling.] [Cf. D. bobbelen, Dan. boble. See Bubble, n.]
   1. To rise in bubbles, as liquids when boiling or agitated;
      to contain bubbles.
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            The milk that bubbled in the pail.    --Tennyson.
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   2. To run with a gurgling noise, as if forming bubbles; as, a
      bubbling stream. --Pope.
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   3. To sing with a gurgling or warbling sound.
      [1913 Webster]

            At mine ear
            Bubbled the nightingale and heeded not. --Tennyson.
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WordNet (r) 3.0 (2006):

bubble
    n 1: a hollow globule of gas (e.g., air or carbon dioxide)
    2: a speculative scheme that depends on unstable factors that
       the planner cannot control; "his proposal was nothing but a
       house of cards"; "a real estate bubble" [syn: house of
       cards, bubble]
    3: an impracticable and illusory idea; "he didn't want to burst
       the newcomer's bubble"
    4: a dome-shaped covering made of transparent glass or plastic
    v 1: form, produce, or emit bubbles; "The soup was bubbling"
    2: flow in an irregular current with a bubbling noise; "babbling
       brooks" [syn: ripple, babble, guggle, burble,
       bubble, gurgle]
    3: rise in bubbles or as if in bubbles; "bubble to the surface"
    4: cause to form bubbles; "bubble gas through a liquid"
    5: expel gas from the stomach; "In China it is polite to burp at
       the table" [syn: burp, bubble, belch, eruct]

Moby Thesaurus II by Grady Ward, 1.0:

241 Moby Thesaurus words for "bubble":
   air, air pocket, airy hope, airy nothing, apparition, autism,
   babble, ball, balloon, be enthusiastic, bilge, bladder, blain,
   bleb, blister, blob, blubber, boil, boil over, boll, bolus, boss,
   bow, brainchild, bubble over, bubble up, bubbles, bulb, bulbil,
   bulblet, bulge, bulla, bump, bunch, burble, burl, button, cahot,
   carbonation, carry on over, chaff, chimera, china, chine, chip,
   churn, clump, cobweb, condyle, convex, cork, daydream, deception,
   delirium, deluded belief, delusion, dereism, dowel, down, dream,
   dream vision, dreamland, dreamworld, droplet, dust, ear,
   effervesce, effervescence, eggshell, eidolon, ellipsoid, enthuse,
   ephemera, ephemeral, ephemerid, ephemerides, ephemeris, ether,
   fairy, false belief, fancy, fantasque, fantasy, feather, ferment,
   fiction, figment, fizz, fizzle, flange, flap, flue, fluff, foam,
   froth, fuzz, gall, geoid, glass, glass house, globe, globelet,
   globoid, globule, glomerulus, gnarl, go on over, gob, gobbet,
   golden dream, gossamer, guggle, gurgle, gush, gush over,
   hallucination, handle, hill, hiss, house of cards, hump, hunch,
   ice, idle fancy, ignis fatuus, illusion, imagery, imagination,
   imagining, insubstantial image, invention, jog, joggle, knob, knot,
   knur, knurl, lap, lather, lip, loop, lump, maggot, make much of,
   make-believe, matchwood, mayfly, misbelief, misconception, mist,
   moil, mole, mote, mountain, myth, nevus, nub, nubbin, nubble,
   oblate spheroid, old paper, orb, orbit, orblet, papilloma,
   parchment, peg, pellet, phantasm, phantom, piecrust, pipe,
   pipe dream, plash, plop, prolate spheroid, purl, quixotic ideal,
   rainbow, rave, rave about, rhapsodize, rib, ridge, ring, ripple,
   romance, rondure, seethe, self-deceit, self-deception,
   self-delusion, shadow, shoulder, sick fancy, simmer, slosh, smoke,
   smolder, snows of yesteryear, sparkle, sphere, spheroid, spherule,
   spine, spirit, splash, sponge, spume, stir, straw, stud, style,
   suds, swash, swish, tab, take on over, thick-coming fancies,
   thin air, thistledown, trick, trill, trip, tubercle, tubercule,
   unreal hope, utopia, vapor, verruca, vesicle, vision, wale, wart,
   wash, welt, whim, whimsy, wildest dreams, work, wrong impression