▪ I. fluid, a. and n.
(ˈfluːɪd)
Also 7 fluide.
[a. Fr. fluide, ad. L. fluid-us, f. fluĕre to flow; see -id.]
A. adj.
1. a. Having the property of flowing; consisting of particles that move freely among themselves, so as to give way before the slightest pressure. (A general term including both gaseous and liquid substances.) fluid extract (U.S.), a concentrated solution (usu. in alcohol) of the active principle of a vegetable drug prepared to a standard strength (see esp. quot. 1965); freq. as fluidextract.
| 1603 Holland Plutarch's Mor. 1361 To..presse together that which of the owne nature is fluid and runneth out. 1638 Wilkins New World i. xii. (1640) 178 The appearance of the milky way dos not arise from some fluider parts of the heaven (as he supposes). 1667 Milton P.L. vi. 349 Spirits..Cannot..mortal wound Receive, no more then can the fluid air. 1711 Pope Temp. Fame 447 Thro' undulating air the sounds are sent, And spread o'er all the fluid element. 1756 C. Lucas Ess. Waters III. 315 The salt fuses readily, and runs very fluid. 1845 Darwin Voy. Nat. xxi. (1852) 493 Masses of lava have been shot through the air whilst fluid. 1851 Wood & Bache Dispens. U.S.A. (ed. 9) 991 Mix thoroughly with the resulting Fluid Extract the Tincture of Ginger. 1885 Buck's Handbk. Med. Sci. I. 783/1 The Aromatic Fluid Extract (Extractum Aromaticum Fluidum, U.S. Ph.). 1935 C. Solomon Prescription Writing & Formulary ii. xi. 102 Fluidextracts (called liquidextracts in the B.P.) are liquid alcoholic preparations of drugs so prepared that 1 cc. contains 1 gram of the drug (or, 1 minim contains 1 grain). 1951 A. Grollman Pharmacol. & Therapeutics i. 38 The tinctures and fluid extracts are the most commonly used liquid preparations. 1965 Pharmacopeia U.S.A. (ed. 17) 787/2 Fluidextracts are liquid preparations of vegetable drugs, containing alcohol as a solvent or as a preservative, or both, and so made that each ml. contains the therapeutic constituents of 1 Gm. of the standard drug that it represents. |
b. fig. and of non-physical things: Flowing or moving readily; not solid or rigid; not fixed, firm, or stable.
| 1642 H. More Song of Soul i. ii. iv, So fluid chance is set its certain bound. 1672 Cave Prim. Chr. ii. ii. (1673) 31 The fluid and transitory condition of man's life. 1719 De Foe Crusoe II. i. 290 The French, whose Temper is allowed to be more volatile..and their Spirits more fluid than in other Nations. 1873 M. Arnold Lit. & Dogma (1876) p. xv, The language of the Bible is fluid, passing, and literary, not rigid, fixed, and scientific. 1885 Academy 6 June 400/1 A time when the Evangelical tradition was still fluid. 1949 Koestler Promise & Fulfilment xiv. 159 This phase of fluid guerilla fighting ended on April 2. 1956 A. Huxley Let. 10 Jan. (1969) 784 Fluid staging, as I remember, used to be all the rage in Germany and Belgium thirty-five years ago. 1959 Times 11 June 3/3 The position, as the scores suggest, is decidedly fluid. |
2. Of speech, etc.: Flowing easily and clearly.
† Of a speaker: Fluent.
| 1691 Wood Ath. Oxon. (1815) II. 219 He [Edmund Bunney] was the most fluid preacher in the reign of qu. Elizabeth, for he seldom or never studied for what he was to deliver, but would preach and pray extempore. c 1789 Gibbon Mem. Misc. Wks. 1796 I. 159 Monsignor Stonor..discovers much venom in the fluid and nervous style of Gibbon. |
B. n. 1. a. A substance whose particles move freely among themselves, so as to give way before the slightest pressure.
Fluids are divided into liquids, which are incompletely elastic, and gases, which are completely so.
| 1661 Boyle Spring of Air i. iv. (1682) 10 The air being a fluid. a 1721 J. Keill Maupertuis' Diss. iii. (1734) 19 Descartes to account for the Revolutions of the Planets around the Sun, supposes them imerged in a Fluid, which [etc.]. 1807 Med. Jrnl. XVII. 275 From the first he swallowed fluids with difficulty. 1813 Sir H. Davy Agric. Chem. i. (1814) 13 Mr. Cavendish made the grand discovery that it [water] was composed of two elastic fluids or gases. 1882 Minchin Unipl. Kinemat. vi. heading, Kinematics of Fluids. |
b. spec. Any liquid constituent or secretion of the body (or of a plant).
| 1704 F. Fuller Med. Gymn. Pref., Moderate exercise will enrich the Fluids. 1732 Arbuthnot Rules of Diet 259 They..act strongly both on the Fluids and Solids. 1804 Knight in Phil. Trans. 186 Gravitation will act on the fluid descending from the leaves. 1831 R. Knox Cloquet's Anat. 3 The fluids constitute the greater part of the organs. 1844 Hoblyn Dict. Med., Fluid of Cotunnius, a thin gelatinous fluid, found in the bony cavities of the labyrinth of the ear. 1878 L. P. Meredith Teeth 49 They decay on account of the bad condition of the fluids of the mouth. |
2. One of several subtle, imponderable, all-pervading substances, whose existence has been assumed to account for the phenomena of heat, magnetism, and electricity.
| 1750 Franklin Lett. Wks. 1840 V. 246 The particles of the electrical fluid. 1832 Nat. Philos., Magnetism iv. §152. 36 (Useful Knowl. Soc.) The supposition, that its phenomena are occasioned by the agency of two magnetic fluids, residing in the particles of iron..They have been denominated respectively the Austral and Boreal fluids. 1881 Maxwell Electr. & Magn. I. 39 In most expositions of this theory the two electricities are called ‘Fluids’. |
3. Comb. (also in sense of
fluidic a. 3) as
fluid-containing adj.; also
fluid amplifier, a fluidic device in which small changes in a low-energy flow of fluid produce corresponding changes in a much larger flow;
fluid circuit, a system of tubes, nozzles, and cavities designed to perform a fluidic function in a way analogous to an electrical circuit;
fluid clutch = fluid drive;
fluid compass,
lens (see
quots.);
fluid compression, compression of steel while in a fluid state; so
fluid-compressed adj.;
fluid coupling, a device that makes use of oil or some other liquid to transmit torque from one shaft to another;
fluid drive, a transmission in a motor vehicle, etc., in which a fluid coupling is used to transmit the power from the engine to the gears;
fluid flywheel = fluid coupling;
fluid logic, the performance of logical operations by fluidic devices; fluidics;
fluid mechanics, the branch of mechanics dealing with the flow of liquids and gases and the way they respond to and exert forces;
fluid pressure, pressure of a fluid, or resembling that of a fluid, being equal in all directions about a point and acting perpendicularly to any surface.
| 1960 Product Engin. 14 Mar. 17/1 Oil or air circuits may soon compete for control applications previously thought suitable only for electronic and electrical controls. Reason: a simple new *fluid amplifier just unveiled at the Army's Diamond Ordnance Fuse Laboratories here. 1963 S.A.E. Jrnl. Aug. 38 Fluid amplifiers perform electronic-like functions. |
| 1964 Control Engin. Sept. 92/2 (heading) Fabricating pure *fluid circuits. 1965 New Scientist 9 Dec. 719/1 Last year..an F-101B fighter was flown with stability against yaw under fluid-circuit control. 1966 Ibid. 24 Mar. 766/3 Fluid circuits, the gas or liquid analogues of electronic circuits, are much slower than their electronic counterparts. |
| 1951 Engineering 26 Oct. 533/3 The transmission assembly..incorporates a *fluid clutch. 1963 R. F. Webb Motorists' Dict. 58 A fluid clutch is..operated by engine speeds through two propellers (turbos) facing each other in a fluid filled container. |
| 1867 Smyth Sailor's Word-bk., *Fluid compass, that in which the card revolves in its bowl floated by alcohol. |
| 1888 Lockwood's Dict. Mech. Engin. 146 *Fluid Compressed Steel. |
| 1884 W. H. Greenwood Steel & Iron xxii. 510 The moulds employed in Sir Joseph Whitworth's process of *fluid compression are of special construction. |
| 1753 N. Torriano Non-Naturals 50 The *Fluid-containing Vessels. |
| 1940 Automobile Engin. 50/3 An oil pump maintains pressure in the *fluid coupling. 1966 McGraw-Hill Encycl. Sci. & Technol. V. 335/1 Because the fluid flow cannot change abruptly, a fluid coupling absorbs rather than transmits shock loads. |
| 1941 Automobile Engin. XXXI. 49/1 *Fluid drive is available as special equipment on Dodges with conventional transmission and clutch. 1968 Jane's Surface Skimmer Systems 1967–68 31/1 The two propulsion engines drive the propellers through a fluid drive system, a reversing gearbox and 1:1 ratio vee box. |
| 1930 Autocar 5 Sept. 1 (Advt.), The Daimler transmission system, comprising the Daimler *fluid flywheel and a self-changing silent four-speed gear⁓box. 1967 E. Rudinger Consumer's Car Gloss. (ed. 2) 44 The fluid flywheel was used originally in place of a clutch in cars with a pre-selector gearbox..and it is now used in some types of automatic transmission. |
| 1874 Knight Dict. Mech. I. 891/1 *Fluid-lens, one in which a liquid is imprisoned between circular glass disks of the required curvatures. |
| 1960 J. R. Greenwood B.S. Thesis, Mass. Inst. Tech. (title) The design and development of a *fluid logic element. 1963 Trans. Soc. Instrument Technol. XV. 123/2 Fluid devices..without movable parts originated much more recently and the interest in fluid logic is due mainly to these types of devices. 1965 Times 23 July 17/3 In a fluid logic system a switch is activated when a small jet of air impinges on another's path. |
| 1937 A. H. Jameson (title) An introduction to *fluid mechanics. 1937 O'Brien & Hickox Applied Fluid Mech. p. ix, Fluid mechanics not only treats the external forces acting on a fluid but also recognizes the internal forces, such as those caused by viscosity, which may markedly affect the motion. 1967 Condon & Odishaw Handbk. Physics (ed. 2) iii. i. 3/1 The entire subject falls into three parts, solid mechanics, fluid mechanics, and, for intermediate states, rheology. 1974 Encycl. Brit. Macropædia XI. 779/2 Fluid mechanics deals with the forces exerted on a fluid to hold it at rest, as well as with the interplay of forces between a fluid and boundaries that cause motion of the fluid. |
| 1845 Rep. Brit. Assoc. 1844 i. 348 To show how..each of the individual particles of water..shall unite in the production of an aggregate motion consistent with the continuity of mass and with the laws of *fluid pressure,—this is a problem which belongs to the mathematician. 1858 W. J. M. Rankine Man. Appl. Mech. 100 The term fluid pressure is used to denote a thrust which is normal and equally intense in all directions round a point. 1910 Encycl. Brit. XIV. 117/1 This mechanical axiom of the normality of fluid pressure is the foundation of the mathematical theory of hydrostatics. 1940 J. D. Jevons Metallurgy of Deep Drawing & Pressing ix. 311 With fluid-pressure actuation the applied pressure cannot rise above a value determined by a release valve. |
▪ II. fluid obs. Sc. form of
flood.