bubble

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A thin, usually spherical or hemispherical film of liquid filled with air or gas.
• noun A globular body of air or gas formed within a liquid.
• noun A pocket formed in a solid by air or gas that is trapped, as during cooling or hardening.
• noun The sound made by the forming and bursting of bubbles.
• noun Something insubstantial, groundless, or ephemeral, especially a fantastic or impracticable idea or belief.
• noun Something light or effervescent.
• noun A usually transparent glass or plastic dome.
• noun A protective, often isolating envelope or cover.
• noun A usually oval outline, as on a ballot or a standardized test form, intended to be filled in using a pencil or pen.
• noun A rounded or irregularly shaped outline containing the words that a character in a cartoon is represented to be saying.
• noun Economics An increase in the price of a commodity, investment, or market that is not warranted by economic fundamentals and is usually caused by ongoing investment or speculation in the expectation that the price will increase further.
• intransitive verb To form or give off bubbles.
• intransitive verb To move or flow with a gurgling sound.
• intransitive verb To rise to the surface.
• intransitive verb To become active or intense enough to come into prominence.
• intransitive verb To display irrepressible activity or emotion.
• adjective Capable of being categorized in one class or another; borderline.
• idiom (on the bubble) On the brink of a new development or condition, especially in danger of being cut from a sports team.

from The Century Dictionary.

• noun Snot.
• To rise in bubbles, as liquors when boiling or agitated; send up bubbles.
• To run with a gurgling noise; gurgle: as, “bubbling fountains,”
• To utter a bubbling or gurgling cry.
• To cause to bubble.
• To cheat; deceive or impose on; hoodwink; bamboozle.
• noun A small vesicle of water or other fluid inflated with air or other gas, and floating on the surface of the fluid.
• noun A small globule of air or other gas in or rising through a liquid.
• noun The vesicle of air in the glass spirit-tube of a mechanics' level.
• noun One of the small hollow beads of glass formerly used for testing the strength of spirits by the rate at which they rise after being plunged in them. See bead, 7.
• noun Anything that wants firmness, substance, or permanence; that which is more specious than real; a vain project; a false show; a delusion; a trifle.
• noun An inflated speculation; a delusive commercial project, especially one which is put forward as insuring extraordinary profits; hence, a financial imposition or fraud; a cheating trick: as, the South Sea bubble. See below.
• noun . A person deceived by an empty project; a dupe.
• noun In New England, hash or minced meat.
• To shed tears in a sniveling, blubbering, childish way.

from the GNU version of the Collaborative International Dictionary of English.

• noun A thin film of liquid inflated with air or gas.
• noun A small quantity of air or gas within a liquid body.
• noun A globule of air, or globular vacuum, in a transparent solid.
• noun A small, hollow, floating bead or globe, formerly used for testing the strength of spirits.
• noun The globule of air in the spirit tube of a level.
• noun 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.
• noun obsolete A person deceived by an empty project; a gull.
• intransitive verb To rise in bubbles, as liquids when boiling or agitated; to contain bubbles.
• intransitive verb To run with a gurgling noise, as if forming bubbles.
• intransitive verb To sing with a gurgling or warbling sound.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A spherically contained volume of air, especially one made from soapy liquid.
• noun A small spherical cavity in a solid material.
• noun Anything resembling a hollow sphere.