| UC | ulcerative colitis; ultracentrifugal; umbilical cord; unchanged; unclassifiable; unconscious; undiff... |
|---|---|
| PCA | para-chloramphetamine; parietal cell antibody; passive cutaneous anaphylaxis; patient care assistant... |
| PCL | pacing cycle length; persistent corpus luteum; plasma cell leukemia; posterior chamber lens; posteri... |
| PD | Doctor of Pharmacy; Dublin Pharmacopoeia; interpupillary distance; Paget disease; pancreatic duct; p... |
| PICA | percutaneous transluminal coronary angioplasty; Porch Index of Communicative Abilities; posterior in... |
| air | 1. The fluid which we breathe, and which surrounds the earth; the atmosphere. It is invisible, inodourous, insipid, transparent, compressible, elastic, and ponderable. By the ancient philosophers, air was regarded as an element; but modern science has shown that it is essentially a mixture of oxygen and nitrogen, with a small amount of carbon dioxide, the average proportions being, by volume: oxygen.96 per cent.; nitrogen.00 per cent.; carbon dioxide.04 per cent. These proportions are subject to a very slight variability. Air also always contains some vapor of water. 2. Symbolically: Something unsubstantial, light, or volatile. "Charm ache with air." "He was still all air and fire. (Macaulay). [Air and fire being the finer and quicker elements as opposed to earth and water]" 3. A particular state of the atmosphere, as respects heat, cold, moisture, etc, or as affecting the sensations; as, a smoky air, a damp air, the morning air, etc. 4. Any aeriform body; a gas; as, oxygen was formerly called vital air. 5. Air in motion; a light breeze; a gentle wind. "Let vernal airs through trembling osiers play." (Pope) 6. Odouriferous or contaminated air. 7. That which surrounds and influences. "The keen, the wholesome air of poverty." (Wordsworth) 8. Utterance abroad; publicity; vent. "You gave it air before me." (Dryden) 9. Intelligence; information. 10. A musical idea, or motive, rhythmically developed in consecutive single tones, so as to form a symmetrical and balanced whole, which may be sung by a single voice to the stanzas of a hymn or song, or even to plain prose, or played upon an instrument; a melody; a tune; an aria. In harmonised chorals, psalmody, part songs, etc, the part which bears the tune or melody in modern harmony usually the upper part is sometimes called the air. 11. The peculiar look, appearance, and bearing of a person; mien; demeanor; as, the air of a youth; a heavy air; a lofty air. "His very air." 12. Peculiar appearance; apparent character; semblance; manner; style. "It was communicated with the air of a secret." (Pope) 12. An artificial or affected manner; show of pride or vanity; haughtiness; as, it is said of a person, he puts on airs. 14. The representation or reproduction of the effect of the atmospheric medium through which every object in nature is viewed. Carriage; attitude; action; movement; as, the head of that portrait has a good air. 15. The artificial motion or carriage of a horse. 16. To expose to the air for the purpose of cooling, refreshing, or purifying; to ventilate; as, to air a room. "It were good wisdom . . . That the jail were aired." (Bacon) "Were you but riding forth to air yourself." (Shak) 17. To expose for the sake of public notice; to display ostentatiously; as, to air one's opinion. "Airing a snowy hand and signet gem." (Tennyson) 18. To expose to heat, for the purpose of expelling dampness, or of warming; as, to air linen; to air liquors. Air is much used adjectively or as the first part of a compound term. In most cases it might be written indifferently, as a separate limiting word, or as the first element of the compound term, with or without the hyphen; as, air bladder, air-bladder, or airbladder; air cell, air-cell, or aircell; air-pump, or airpump. Air balloon. See Balloon. Air bath. An apparatus for the application of air to the body. An arrangement for drying substances in air of any desired temperature. Air castle. See Castle in the air, under Castle. Air compressor, a machine for compressing air to be used as a motive power. Air crossing, a passage for air in a mine. Air cushion, an air-tight cushion which can be inflated; also, a device for arresting motion without shock by confined air. Air fountain, a contrivance for producing a jet of water by the force of compressed air. Air furnace, a furnace which depends on a natural draft and not on blast. Air line, a straight line; a bee line. Hence Air-line,; as, air-line road. <medicine> Air lock Unsupported and liable to be turned or taken in flank; as, the army had its wing in the air. To take air, to be divulged; to be made public. To take the air, to go abroad; to walk or ride out. Origin: OE. Air, eir, F. Air, L. Aer, fr. Gr, air, mist, for, fr. Root to blow, breathe, probably akin to E. Wind. In sense 10 the French has taking a meaning fr. It. Aria atmosphere, air, fr. The same Latin word; and in senses 11, 12, 13 the French meaning is either fr. L. Aria, or due to confusion with F. Aire, in an older sense of origin, descent. Cf. Ary, Debonair, Malaria, Wind. Source: Websters Dictionary (01 Mar 1998) |
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| air ambulances | Fixed-wing aircraft or helicopters equipped for air transport of patients. (12 Dec 1998) |
| air bags | Automotive safety devices consisting of a bag designed to inflate upon collision and prevent passengers from pitching forward. (12 Dec 1998) |
| air bladder | 1. <anatomy> An air sac, sometimes double or variously lobed, in the visceral cavity of many fishes. It originates in the same way as the lungs of air-breathing vertebrates, and in the adult may retain a tubular connection with the pharynx or oesophagus. 2. A sac or bladder full of air in an animal or plant; also an air hole in a casting. Source: Websters Dictionary (01 Mar 1998) |
| air-bone gap | The difference between the threshold for hearing acuity by bone conduction and by air conduction. (05 Mar 2000) |
| air bronchogram | Radiographic appearance of an air-filled bronchus surrounded by fluid-filled airspaces. (05 Mar 2000) |
| air cell | 1. <botany> A cavity in the cellular tissue of plants, containing air only. 2. <anatomy> A receptacle of air in various parts of the system; as, a cell or minute cavity in the walls of the air tubes of the lungs; the air sac of birds; a dilatation of the air vessels in insects. Source: Websters Dictionary (01 Mar 1998) |
| air chamber | 1. A chamber or cavity filled with air, in an animal or plant. 2. A cavity containing air to act as a spring for equalizing the flow of a liquid in a pump or other hydraulic machine. Source: Websters Dictionary (01 Mar 1998) |
| air-conditioner lung | An extrinsic allergic alveolitis caused by forced air contaminated by thermophilic actinomycetes and other organisms. (05 Mar 2000) |
| air conditioning | The maintenance of certain aspects of the environment within a defined space to facilitate the function of that space; aspects controlled include air temperature and motion, radiant heat level, moisture, and concentration of pollutants such as dust, microorganisms, and gases. (12 Dec 1998) |
| air conduction | In relation to hearing, the transmission of sound to the inner ear through the external auditory canal and the structures of the middle ear. (05 Mar 2000) |
| air contrast barium enema | A double contrast enema in which air is introduced after coating of the colon with a dense barium suspension for radiographic study. Synonym: air contrast barium enema. (05 Mar 2000) |
| air contrast enema | A double contrast enema in which air is introduced after coating of the colon with a dense barium suspension for radiographic study. Synonym: air contrast barium enema. (05 Mar 2000) |
| air dose | The radiation dose, expressed in roentgens, delivered at a point in free air. Synonym: air dose. (05 Mar 2000) |
| air drill | <equipment> A drill driven by the elastic pressure of condensed air; a pneumatic drill. (06 Aug 1998) |