[air] 
| 1. | a mixture of nitrogen, oxygen, and minute amounts of other gases that surrounds the earth and forms its atmosphere. |
| 2. | a stir in the atmosphere; a light breeze. |
| 3. | overhead space; sky: The planes filled the air. |
| 4. | circulation; publication; publicity: to give air to one's theories. |
| 5. | the general character or complexion of anything; appearance: His early work had an air of freshness and originality. |
| 6. | the peculiar look, appearance, and bearing of a person: There is an air of mystery about him. |
| 7. | airs, affected or unnatural manner; manifestation of pride or vanity; assumed haughtiness: He acquired airs that were insufferable to his friends. |
| 8. | Music.
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| 9. | aircraft as a means of transportation: to arrive by air; to ship goods by air. |
| 10. | Informal. air conditioning or an air-conditioning system: The price includes tires, radio, and air. |
| 11. | Radio. the medium through which radio waves are transmitted. |
| 12. | Archaic. breath. |
| 13. | to expose to the air; give access to the open air; ventilate (often fol. by out): We air the bedrooms every day. |
| 14. | to expose ostentatiously; bring to public notice; display: to air one's opinions; to air one's theories. |
| 15. | to broadcast or televise. |
| 16. | to be exposed to the open air (often fol. by out): Open the window and let the room air out. |
| 17. | to be broadcast or televised. |
| 18. | operating by means of air pressure or by acting upon air: an air drill; an air pump. |
| 19. | of or pertaining to aircraft or to aviation: air industry. |
| 20. | taking place in the air; aerial: air war. |
| 21. | clear the air, to eliminate dissension, ambiguity, or tension from a discussion, situation, etc.: The staff meeting was intended to help clear the air. |
| 22. | get the air, Informal.
|
| 23. | give (someone) the air, Informal.
|
| 24. | in the air, in circulation; current: There's a rumor in the air that we're moving to a new location. |
| 25. | into thin air, completely out of sight or reach: He vanished into thin air. |
| 26. | off the air,
|
| 27. | on the air,
|
| 28. | put on airs, to assume an affected or haughty manner: As their fortune increased, they began to put on airs. |
| 29. | take the air,
|
| 30. | up in the air,
|
| 31. | walk or tread on air, to feel very happy; be elated. |
r) the lower atmosphere; conflated with (especially for defs. 4 and 5) F air, OF aire nature, character < L ager field (cf. acre ) and ārea threshing floor, clearing, area; and with (for def. 7) F air < It aria aria 
air (âr)
n.
A colorless, odorless, tasteless, gaseous mixture, approximately 78 percent nitrogen and approximately 21 percent oxygen with lesser amounts of argon, carbon dioxide, hydrogen, neon, helium, and other gases.
This mixture, with varying amounts of moisture and particulate matter, enveloping Earth; the atmosphere.
Any of various respiratory gases. No longer in technical use.
| air (âr) Pronunciation Key
The colorless, odorless, tasteless mixture of gases that surrounds the Earth. Air consists of about 78 percent nitrogen and 21 percent oxygen, with the remaining part made up mainly of argon, carbon dioxide, neon, helium, methane, and krypton in decreasing order of volume. Air also contains varying amounts of water vapor, particulate matter such as dust and soot, and chemical pollutants. |
into thin air
Also, into the blue. Completely disappeared, as in The report was here on my desk and now it's gone, vanished into thin air, or I don't know where they've gone
into the blue, for all I know. Both of these hyperbolic expressions, often preceded by vanish as in the first example, use the rarefied atmosphere far above the earth as a metaphor for an unknown location. Shakespeare wrote of ghosts that "melted . . . into thin air" (The Tempest, 4:1). An antonym for both is out of thin air, meaning "from an unknown place or source." For example, She made up this excuse out of thin air, or The car appeared out of thin air. However, out of the blue is not precisely an antonym (see under out of a clear blue sky).