vapor

1. (idiomatic) Something insubstantial, fleeting, or transitory; unreal fancy; vain imagination; idle talk; boasting.Examples: "For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away."; "I am at this present very sick of my little vapour of fame."; "The press operates as a safety-valve for the vapor of popular ebullision."UScountableidiomaticuncountable

2. (dated) Any medicinal agent designed for administration in the form of inhaled vapour.Examples: "Sulphurous fumes have also been recommended, as well as diffusing a variety of vapors in the apartment of the patient; on their beneficial or injurious effects we are unable to speak."; "Hence the vapor, so useful in expanding the compressed tissues and enabling the air to permeate and expand the contracted parenchyma in consumption, causes a sensation of great fatigue in asthma."; "Professor Matthews has at length the pleasure, after much unaboidable delay, of respectfully announcin to the Faculty, that he is prepared to fill their prescriptions by any practicable formula, in the use of his new method of applying medicinal vapors to the lungs, air-passages, & c., by means of the Multiform Fumigator ."UScountabledateduncountable

3. (archaic, in the plural) Hypochondria; melancholy; the blues; hysteria, or other nervous disorder.Examples: "Jan 13, 1732, John Arbuthnot, letter to Jonathan Swift He talks me into a fit of vapours twice or thrice a week."; "She made several gulps and controlled her breath. She released her grip on Podson and stared at him without recognition. Podson went on patting her reassuringly, relieved from administering first aid to an attack of the vapours."USarchaiccountablein-pluraluncountable

4. (obsolete) Wind; flatulence.Examples: "The surcharge of the stomack from a gross vapour, and from the poise of some outward weight, are alike"UScountableobsoleteuncountable