Dou·ble a.
 1. Twofold; multiplied by two; increased by its equivalent; made twice as large or as much, etc.
    Let a double portion of thy spirit be upon me.   -- 2 Kings ii. 9.
    Darkness and tempest make a double night.   --Dryden.
 2. Being in pairs; presenting two of a kind, or two in a set together; coupled.
 [Let] The swan, on still St. Mary's lake,
 Float double, swan and shadow.   --Wordsworth.
 3. Divided into two; acting two parts, one openly and the other secretly; equivocal; deceitful; insincere.
    With a double heart do they speak.   -- Ps. xii. 2.
 4. Bot. Having the petals in a flower considerably increased beyond the natural number, usually as the result of cultivation and the expense of the stamens, or stamens and pistils. The white water lily and some other plants have their blossoms naturally double.
 Note: ☞ Double is often used as the first part of a compound word, generally denoting two ways, or twice the number, quantity, force, etc., twofold, or having two.
 Double base, or Double bass Mus., the largest and lowest-toned instrument in the violin form; the contrabasso or violone.
 Double convex. See under Convex.
 Double counterpoint Mus., that species of counterpoint or composition, in which two of the parts may be inverted, by setting one of them an octave higher or lower.
 Double court Lawn Tennis, a court laid out for four players, two on each side.
 Double dagger Print., a reference mark (‡) next to the dagger (†) in order; a diesis.
 Double drum Mus., a large drum that is beaten at both ends.
 Double eagle, a gold coin of the United States having the value of 20 dollars.
 Double entry. See under Bookkeeping.
 Double floor Arch., a floor in which binding joists support flooring joists above and ceiling joists below. See Illust. of Double-framed floor.
 Double flower. See Double, a., 4.
 Double-framed floor Arch., a double floor having girders into which the binding joists are framed.
 Double fugue Mus., a fugue on two subjects.
 Double letter. (a) Print. Two letters on one shank; a ligature. (b) A mail requiring double postage.
 Double note Mus., a note of double the length of the semibreve; a breve. See Breve.
 Double octave Mus., an interval composed of two octaves, or fifteen notes, in diatonic progression; a fifteenth.
 Double pica. See under Pica.
 Double play Baseball, a play by which two players are put out at the same time.
 Double plea Law, a plea alleging several matters in answer to the declaration, where either of such matters alone would be a sufficient bar to the action. --Stephen.
 Double point Geom., a point of a curve at which two branches cross each other. Conjugate or isolated points of a curve are called double points, since they possess most of the properties of double points (see Conjugate). They are also called acnodes, and those points where the branches of the curve really cross are called crunodes. The extremity of a cusp is also a double point.
 Double quarrel. Eccl. Law See Duplex querela, under Duplex.
 Double refraction. Opt. See Refraction.
 Double salt. Chem. (a) A mixed salt of any polybasic acid which has been saturated by different bases or basic radicals, as the double carbonate of sodium and potassium, NaKCO3.6H2O. (b) A molecular combination of two distinct salts, as common alum, which consists of the sulphate of aluminium, and the sulphate of potassium or ammonium.
 Double shuffle, a low, noisy dance.
 Double standard Polit. Econ., a double standard of monetary values; i. e., a gold standard and a silver standard, both of which are made legal tender.
 Double star Astron., two stars so near to each other as to be seen separate only by means of a telescope. Such stars may be only optically near to each other, or may be physically connected so that they revolve round their common center of gravity, and in the latter case are called also binary stars.
 Double time Mil.. Same as Double-quick.
 Double window, a window having two sets of glazed sashes with an air space between them.