a. and sb. [ad. med. or mod.L. trājectōri-us pertaining to trajection (cf. late L. trājectōrium a funnel, c. 400), whence F. trajectoire ‘casting … conveying through or over’ (Cotgr., 1611); f. L. trāject-: see TRAJECT v., and -ORY. The sb. corresponds to L. trājectōria (Newton) fem., in F. trajectoire sb. (in Cotgr.).]
A. adj. 1. Physics. Of or pertaining to that which is thrown or hurled through the air or space.
1668. Phil. Trans., III. 807. To explaine that Trajectory rectilinear motion, he subjects the Comet of A. 1652 to a very rigid Calculus.
1851–9. Mallet, in Man. Sci. Enq., 349. Reach the ground after describing a trajectory path.
2. Physiol. Said of a gland into which lymphatic vessels convey their fluids. ? Obs.
1747. trans. Astruc’s Fevers, 132. The common receptacles or trajectory glands of several lymphatic vessels.
B. sb. 1. Physics. The path of any body moving under the action of given forces; by many modern writers restricted to that of a body not known to be moving, like a planet, in a closed curve or orbit; esp. the curve described by a projectile in its flight through the air.
Hence loosely used by gun-makers for the height to which a bullet rises above the line of sight, as ‘the trajectory of this rifle is one inch in one hundred yards.’
1696. Whiston, Th. Earth, I. (1722), 8. [This] must change its rectilinear into a curvilinear trajectory.
1704. J. Harris, Lex. Techn., I. Trajectory, of a Comet, is the Line which by its Motion it describes.
1726. trans. Gregory’s Astron., I. I. 73. Kepler, and several Philosophers after him, supposed the Trajectories of Comets to be right Lines.
1728. trans. Newton’s Triat. Syst. World, 142. If this problem was resolved, we should thence have a method of determining the trajectories of Comets to the greatest accuracy.
1795. Hutton, Math. Dict., II. 603. Trajectory, a term often used generally for the path of any body moving either in a void, or in a medium that resists its motion…. Trajectory of a Comet is its path or orbit, or the line it describes in its motion.
1828. J. M. Spearman, Brit. Gunner (ed. 2), 395. To determine, by theory, the range of a shot, and the form of its trajectory in the air.
1843. Mill, Logic, VI. x. § 3. There might be others which, instead of an orbit, describe a trajectory, or a course not returning into itself.
1862. H. Spencer, First Princ., II. x. § 82 (1875), 252. It is common to assert that the trajectory of a cannon ball is a parabola.
b. transf. and fig.
1838. Brit. Critic, XXIII. 1. An examination of … the somewhat eccentric trajectory of his [A. Knox’s] thoughts.
1883. Lockyer, in Times, 8 Dec., 10. We have … got a straight trajectory of the abnormal sunsets from the Seychelles to Brazil.
1883. Cornh. Mag., Feb., 217. That majestic spirit passes … through all the upward or downward trajectory between heaven and hell.
1889. Boyd Carpenter, Perm. Elem. Relig., Introd. 27. The trajectory of religion must rush away to the infinite beyond.
2. Geom. A curve or surface passing through a given set of points, or intersecting each of a given series of curves or surfaces according to a given law, e.g., at a constant angle.
1795. Hutton, Math. Dict., II. 603. Newton (Princip. lib. I. prob. 22) proposes to describe a Trajectory that shall pass through five given points.
1816. trans. Lacroix’s Diff. & Int. Calculus, 401. A problem celebrated from the earliest infancy of the Integral Calculus—the problem of Trajectories. Its object is to determine a curve which shall intersect all curves of a given species at a given angle.
1865. B. Price, Infin. Calc. (ed. 2), 606. If the [constant] angle between the two curves is a right angle the trajectory is said to be orthogonal.
3. A projectile, as a bullet. rare.
1861. W. H. Russell, in Times, 29 July. As far as I could judge, the men of the regiment were stout and strong material for arresting trajectories.
