noun

1. 1. visible particles of moisture floating in the air, as fog, mist, or steam
   2. any cloudy or imperceptible exhalation, as smoke or noxious fumes
2. the gaseous form of any substance which is usually a liquid or a solid
3. 1. any substance vaporized for use in machinery, medical therapy, etc.
   2. a mixture of such a vaporized substance with air, as the explosive mixture in an automotive cylinder
4. Now Rare anything insubstantial or worthless
5. Archaic
   1. exhalations from the stomach believed to be harmful to one's health
   2. hypochondria or depressed spirits: often with the

Etymology: ME vapour < Anglo-Fr < MFr vapeur < L vapor < IE base *wep-, to give off vapors

intransitive verb

1. to rise or pass off in the form of vapor; evaporate
2. to give off vapor
3. to indulge in idle talk or boasting

transitive verb