1
: diffused matter (such as smoke or fog) suspended floating in the air and impairing its transparency
2
a
: a substance in the gaseous state as distinguished from the liquid or solid state
b
: a substance (such as gasoline, alcohol, mercury, or benzoin) vaporized for industrial, therapeutic, or military uses
also
: a mixture (such as the explosive mixture in an internal combustion engine) of such a vapor with air
3
a
: something unsubstantial or transitory : phantasm
b
: a foolish or fanciful idea
4
vapors plural
a
archaic
: exhalations of bodily organs (such as the stomach) held to affect the physical or mental condition
b
: a depressed or hysterical nervous condition
vapored; vaporing
ˈvā-p(ə-)riŋ 
1
a
: to rise or pass off in vapor
b
: to emit vapor
2
: to indulge in bragging, blustering, or idle talk
Did you know?
Speakers of the English language, mindful of the lightness and unsubstantiality of floating air and gas, have put several airy words to good use over the years to describe the act of talking idly or boastfully. The earliest such word is blow (as in "he kept blowing about his new job"), which drifted into English sometime about 1400. Vapor wafted into the language in the 1620s, and a little over 200 years later windbags, later also known as gasbags, not only blew and vapored but also gassed about anything they could.
Synonyms
Examples of vapor in a Sentence
Verb
a faded Southern belle tiresomely vaporing about all the handsome beaux she had in her long-ago youth
Recent Examples on the Web
Jeffrey Kluger, TIME, 30 Sep. 2024
The impact would have shot unfathomable quantities of soot and vapor into the atmosphere, shrouding the world below and triggering a widespread die-off.
—Will Sullivan, Smithsonian Magazine, 16 Aug. 2024
Daley Quinn, Health, 26 Apr. 2024
Volatility, even if reduced in new products, means droplets can go from liquid to vapor and travel on the wind, even after spraying.
—The Arizona Republic, 10 Feb. 2024
See all Example Sentences for vapor 
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Noun
In the inner solar system—this side of Jupiter—the proximity of the sun causes both free-floating water and water entrained on bodies like asteroids to flash into vapor.
—Jeffrey Kluger, TIME, 30 Sep. 2024
The impact would have shot unfathomable quantities of soot and vapor into the atmosphere, shrouding the world below and triggering a widespread die-off.
—Will Sullivan, Smithsonian Magazine, 16 Aug. 2024
Verb
Nasal decongestant vapor inhaler: A nasal inhaler is a decongestant formula used to inhale for relief.
—Daley Quinn, Health, 26 Apr. 2024
Volatility, even if reduced in new products, means droplets can go from liquid to vapor and travel on the wind, even after spraying.
—The Arizona Republic, 10 Feb. 2024
See all Example Sentences for vapor
Dictionary Entries Near vapor
Cite this Entry
“Vapor.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/vapor. Accessed 28 Nov. 2024.
Copy CitationMedical Definition
vapor
noun
va·por
variants
or chiefly British vapour
1
a
: a substance in the gaseous state as distinguished from the liquid or solid state
b
: a substance (as alcohol or benzoin) vaporized for industrial, therapeutic, or military uses
2
vapors or chiefly British vapours plural
a
: exhalations of bodily organs (as the stomach) formerly held to affect the physical or mental condition
b
: a depressed or hysterical nervous condition
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