from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Barely visible or cloudy diffused matter, such as mist, fumes, or smoke, suspended in the air.
  • n. The state of a substance that exists below its critical temperature and that may be liquefied by application of sufficient pressure.
  • n. The gaseous state of a substance that is liquid or solid under ordinary conditions.
  • n. The vaporized form of a substance for use in industrial, military, or medical processes.
  • n. A mixture of a vapor and air, as the explosive gasoline-air mixture burned in an internal-combustion engine.
  • n. Archaic Something insubstantial, worthless, or fleeting.
  • n. Archaic A fantastic or foolish idea.
  • n. Archaic Exhalations within a bodily organ, especially the stomach, supposed to affect the mental or physical condition. Used with the.
  • n. Archaic A nervous disorder such as depression or hysteria. Used with the.
  • transitive v. To vaporize.
  • intransitive v. To give off vapor.
  • intransitive v. To evaporate.
  • intransitive v. To engage in idle, boastful talk.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. Cloudy diffused matter such as mist, steam or fumes suspended in the air.
  • n. The gaseous state of a substance that is normally a solid or liquid.
  • v. To become vapor; to be emitted or circulated as vapor.
  • v. To turn into vapor.
  • v. To use insubstantial language; to boast or bluster.

from the GNU version of the Collaborative International Dictionary of English

  • n. Any substance in the gaseous, or aëriform, state, the condition of which is ordinarily that of a liquid or solid.
  • n. In a loose and popular sense, any visible diffused substance floating in the atmosphere and impairing its transparency, as smoke, fog, etc.
  • n. Wind; flatulence.
  • n. Something unsubstantial, fleeting, or transitory; unreal fancy; vain imagination; idle talk; boasting.
  • n. An old name for hypochondria, or melancholy; the blues.
  • n. A medicinal agent designed for administration in the form of inhaled vapor.
  • intransitive v. To pass off in fumes, or as a moist, floating substance, whether visible or invisible, to steam; to be exhaled; to evaporate.
  • intransitive v. To emit vapor or fumes.
  • intransitive v. To talk idly; to boast or vaunt; to brag.
  • transitive v. To send off in vapor, or as if in vapor.

from The Century Dictionary and Cyclopedia

  • To pass off in the form of vapor; dissolve, as into vapor or thin air; be exhaled; evaporate.
  • To give out vapor, steam, or gas; emit vapors or exhalations; exhale; steam.
  • To boast or vaunt; bully; hector; brag; swagger; bounce.
  • To cause to pass into the state of vapor; cause to dissolve or disappear in or as in vapor, gas, thin air, or other unsubstantial thing.
  • To afflict or infect with vapors; dispirit; depress.
  • To bully; hector.
  • n. An exhalation of moisture; any visible diffused substance, as fog, mist, steam, or smoke, floating in the atmosphere and impairing its transparency.
  • n. In physics, the gaseous form which a solid or liquid substance assumes when sufficiently heated.
  • n. Effluence; influence.
  • n. Wind; flatulence.
  • n. In medicine, a class of remedies, officinal in the British pharmacopœia, which are to be applied by inhalation: such as vapor creasoti, a mixture of 12 minims of creosote in 8 fluidounces of boiling water, the vapor of which is to be inhaled.
  • n. Something unsubstantial, fleeting, or transitory; vain imagination; fantastic notion.
  • n. plural A hectoring or bullying style of language or conduct, adopted by ranters and swaggerers with the purpose of bringing about a real or mock quarrel.
  • n. plural A disease of nervous debility in which strange images seem to float hazily before the eyes, or appear as if real; hence, hypochondriacal affections; depression of spirit; dejection; spleen; “the blues”: a term much affected in the eighteenth century, but now rarely used.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the process of becoming a vapor
  • n. a visible suspension in the air of particles of some substance


Middle English vapour, from Anglo-Norman, from Latin vapor.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin vapor ("steam, heat"). (Wiktionary)



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