Usage note

See -or1.


  1. a visible exhalation, as fog, mist, steam, smoke, or noxious gas, diffused through or suspended in the air: the vapors rising from the bogs.
  2. Physics. a gas at a temperature below its critical temperature.
  3. a substance converted into vapor for technical or medicinal uses.
  4. a combination of a vaporized substance and air.
  5. gaseous particles of drugs that can be inhaled as a therapeutic agent.
  6. Archaic.
    1. a strange, senseless, or fantastic notion.
    2. something insubstantial or transitory.
  7. vapors, Archaic.
    1. mental depression or hypochondria.
    2. injurious exhalations formerly supposed to be produced within the body, especially in the stomach.
verb (used with object)
  1. to cause to rise or pass off in, or as if in, vapor; vaporize.
  2. Archaic. to affect with vapors; depress.
verb (used without object)
  1. to rise or pass off in the form of vapor.
  2. to emit vapor or exhalations.
  3. to talk or act grandiloquently, pompously, or boastfully; bluster.
Also especially British, va·pour.

Origin of vapor

1325–75; Middle English vapour < Latin vapor steam
Related formsva·por·a·ble, adjectiveva·por·a·bil·i·ty, nounva·por·er, nounva·por·less, adjectiveva·por·like, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for vapour

Historical Examples of vapour

British Dictionary definitions for vapour


US vapor

  1. particles of moisture or other substance suspended in air and visible as clouds, smoke, etc
  2. a gaseous substance at a temperature below its critical temperatureCompare gas (def. 3)
  3. a substance that is in a gaseous state at a temperature below its boiling point
  4. rare something fanciful that lacks substance or permanence
  5. the vapours archaic a depressed mental condition believed originally to be the result of vaporous exhalations from the stomach
  1. to evaporate or cause to evaporate; vaporize
  2. (intr) to make vain empty boasts; brag
Derived Formsvapourable or US vaporable, adjectivevapourability or US vaporability, nounvapourer or US vaporer, nounvapourish or US vaporish, adjectivevapourless or US vaporless, adjectivevapour-like or US vapor-like, adjectivevapoury or US vapory, adjective

Word Origin for vapour

C14: from Latin vapor


  1. the US spelling of vapour
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for vapour



late 14c., from Anglo-French vapour, from Latin vaporem (nominative vapor) "exhalation, steam, heat," of unknown origin. Vapors "fit of fainting, hysteria, etc." is 1660s, from medieval notion of "exhalations" from the stomach or other organs affecting the brain.

Online Etymology Dictionary, © 2010 Douglas Harper

vapour in Medicine


  1. Barely visible or cloudy diffused matter, such as mist, fumes, or smoke, suspended in the air.
  2. The state of a substance that exists below its critical temperature and that may be liquefied by application of sufficient pressure.
  3. The gaseous state of a substance that is liquid or solid under ordinary conditions.
  4. The vaporized form of a medicinal preparation to be administered by inhalation.
  5. A mixture of a vapor and air, as an explosive mixture of gasoline and air burned in an internal-combustion engine.
  6. vapors Exhalations within an organ, especially the stomach, supposed to affect the mental or physical condition. No longer in technical use.
  7. vapors A nervous disorder such as depression or hysteria. No longer in technical use.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

vapour in Science


  1. The gaseous state of a substance that is normally liquid or solid at room temperature, such as water that has evaporated into the air. See more at vapor pressure. See also water vapor.
  2. A faintly visible suspension of fine particles of matter in the air, as mist, fumes, or smoke.
  3. A mixture of fine droplets of a substance and air, as the fuel mixture of an internal-combustion engine.
Related formsvaporize verb
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.