[ad. med. or mod. L. *undulātio: cf. UNDULATE a. and v., and Sp. undulacion (Pg. -ação), F. ondulation, It. ondulazione.]
1. The action of moving in a wave-like manner; a gentle rising and falling in the manner of waves.
1646. Sir T. Browne, Pseud. Ep., III. xv. 142. Those animals, whose bodies consist of … annulary fibers, and move by undulation, that is, like the waves of the Sea.
1664. Power, Exp. Philos., I. 36. Their motion is … restless and constant, with perpetual undulations and wavings, like Eels or Snakes.
1707. Floyer, Physic. Pulse-Watch, 267. The undulation of the Spirits towards the Brain produces all our Sensations.
1762. Falconer, Shipwreck, I. 308. Soon this transient undulation o’er The sea subsides.
1820. Keats, Hyperion, III. 132. His golden tresses … Kept undulation round his eager neck.
1854. Owen, in Orr’s Circ. Sci., Org. Nat., I. 228. Whales and porpoises progress by bounding movements or undulations in a vertical plane.
1875. Manning, Mission H. Ghost, iv. 106. We are as unstable as … the restless undulation of the water.
transf. 1777. Johnson, Lett., I. 389. Mrs. * * grows old, and has lost much of her undulation and mobility.
b. A wave-like motion of the air, ether, etc., as in the propagation of sound or light.
1658. Phillips, s.v., Undulation of the air.
1672. Phil. Trans., VII. 5148. The other Secondary Affections of Winds; as their Undulation,… Opposition, etc.
1728. Chambers, Cycl., s.v. Sound, A Wave or Undulation of Air.
1764. Reid, Inquiry, iv. § 1. 117. Each undulation must be made up of the advance and recoil of innumerable particles of elastic air.
1802. Young, in Phil. Trans., XCII. 21. The undulations of green light being nearly in the ratio of 61/2.
1870. H. Spencer, Princ. Psych., I. I. iii. 47. Those minute agents that terminate the nerves of the retina are acted on by luminiferous undulations.
Comb. 1838. Whewell, in Todhunter, Acc. Writ. (1876), II. 269. A curious … paper upon the theory of the rainbow treated undulation-wise.
c. transf. Of sound.
1668. Dryden, Ess. Dram. Poesy, ¶ 3. Those little undulations of sound … still seeming to retain somewhat of their first horror.
1705. Addison, Italy, 42. Two parallel Walls that beat the Sound back on each other, till the Undulation is quite worn out.
1791. Mrs. Radcliffe, Rom. Forest, xi. The notes floated on the air in soft undulations.
1851. Froude, Short Stud., Homer (1867), II. 166. The actions of men … crumble away into the softer undulations of prose.
† d. spec. (See quot.) Obs.–1
1676. Grew, Musæum, Anat. Stomach, vi. 35. Vndulation, is when the Contraction is made in several parts of the Stomach successively.
2. A wave-like curve or a series of these; an undulating curvature or sweep.
1670. Evelyn, Sylva (ed. 2), 119. The Root of the wilder sort [is] incomparable for its crisped undulations.
1803. Shaw, Gen. Zool., IV. 497. Scales … edged with yellow, so as to form numerous obliquely transverse undulations over the whole body.
1846. Carpenter, Man. Phys., 186. Minute tubuli,… exhibiting numerous minute undulations, and sometimes more decided curvatures, in their course.
1875. Sir T. Seaton, Fret-Cutting, 36. How … you will turn or bend the stalks, so as to give a natural undulation and appearance to the whole work.
3. The fact of forming or presenting a series of rounded heights and hollows; an undulating rise and fall of level.
1798. S. & Ht. Lee, Canterb. T., II. 441. For many a mile, with graceful undulation, wandered the high road.
1835. Willis, Pencillings, I. xxiv. 167. A continual undulation of rock and sand.
b. An instance of this; also, a single rise and fall of this nature.
1823. Rutter, Fonthill, 86. The undulations of the surface occasionally give a beautiful variety to the scene.
1878. Huxley, Physiogr., 214. Here the strata … have been thrown into a succession of gentle undulations.
