[a. OF. concave, f. concave adj.: cf. L. concava hollows. Appears to be earlier in Eng. than the adj.; but in later uses it is only an absolute use of the adj. Not unfrequently stressed conca·ve by poets.]
† 1. A hollow; a cavity. Obs.
1541. R. Copland, Guydon’s Quest. Chirurg. In the fyrste concaue is receyued the roundnes of Cohas aforesayd.
c. 1590. Marlowe, Faust. (ed. Rtldg.), 95/2. Bred in the concave of some monstrous rock.
1602. Marston, Ant. & Mel., III. Wks. 1856, I. 35. I will warble to the delicious concave of my mistresse eare.
1747. Hooson, Miner’s Dict., W j. [Miners] in the Bowels and Concaves of the Earth.
1814. Cary, Dante’s Inf., IX. 16. Doth ever any Into this rueful concave’s extreme depth Descend?
† b. A cylindrical or spherical cavity; the bore of a gun, etc. Obs.
1597. Daniel, Civ. Wares, VI. xlix. They minerals combustible do find, Which, in stopped concaves placed cunningly, They fire.
1627. Capt. Smith, Seaman’s Gram., xiv. 65. The Sillinder or Concaue … is the bore of the Peece.
1703. Moxon, Mech. Exerc., 54. Then put into the two Concaves a round Bullet, that will just fill them both.
c. A concave part of a machine, as of a thresher.
1874. Knight, Dict. Mech., I. 604/2. The example shows a concave in which each slat rests upon a spring, and the grain escapes through the intervening spaces.
2. A concave surface, or the structure presenting it; a vault, arch, hemisphere, etc., as viewed from the center; often applied to the vault of the sky.
1552. Lyndesay, Monarche, 6247. All dede thyngis corporall, Onder the Concaue of the Heuin Impyre.
16[?]. Evelyn, Mem. (1857), I. 127. The inside, or concave, is covered with most exquisite Mosaic.
1651. H. More, in Enthus. Triumph. (1656), 191. All to the very concave [i.e., ‘sphere’] of the Moon.
1660. Barrow, Euclid, III. viii. Those lines that fall on the concave of the circumference.
1813. Shelley, Q. Mab, 232. The chariot’s way Lay through the midst of an immense concave.
1870. Proctor, Other Worlds, ii. 45. Every single star that shines upon us from the celestial concave.
b. spec. The vault of heaven.
1635. Swan, Spec. M., iv. § 2 (1643), 70. On high within the concave, as are the … starres.
1770. E. Nicklin, in Monthly Rev., 406. Loud clamour rising rends the vast concave.
1808. J. Barlow, Columb., X. 504. Let … all the concave flame in one clear sun.
1864. Skeat, trans. Uhland’s Poems, 21. Around me sprends the blue concave.
† 3. A concave lens, speculum, etc. Obs.
1621. Burton, Anat. Mel., II. ii. IV. (1651), 284. To represent solid bodies, by Cylinders and Concaves, to walk in the air.
1685. Boyle, Effects of Motion, viii. 96. An expert Artificer, that made metalline Concaves.
1797. Brougham, in Phil. Trans., 377. Glass concaves were freer from these hairs.
4. A card prepared for cheating by being cut slightly concave on two edges: cf. quot. 1873.
1825. C. M. Westmacott, English Spy, I. 271. Every leg and Greek who play the concave suit.
1873. Slang Dict., Concaves and convexes, a pack of cards contrived for cheating, by cutting all the cards from the two to the seven concave, and all from the eight to the king convex. Then by cutting the pack breadthwise a convex card is cut, and by cutting it lengthwise a concave is secured.
