a. [f. L. crepuscul-um + -AR. Cf. F. crépusculaire.]
1. Of or pertaining to twilight.
1755. B. Martin, Mag. Arts & Sc., I. i. 3. The Difference … between the crepuscular and the Noon-tide Light.
1791. E. Darwin, Bot. Gard., I. Notes 12. The crespuscular atmosphere, or the region where the light of the sun ceases to be refracted to us, is estimated … to be between 40 and 50 miles high.
1876. G. F. Chambers, Astron., 67. A faint crepuscular light extending beyond the cusps of the planet.
2. fig. Resembling or likened to twilight; dim, indistinct.
1668. Phil. Trans., III. 730. And perhaps I might have lost the Crepuscular remains of my Sight.
1860. J. P. Kennedy, W. Wirt, II. ix. 157. [The law is] at best, a crepuscular labyrinth.
1879. H. James, Hawthorne, 132. The crepuscular realm of the writer’s own reveries.
b. esp. Resembling or likened to the morning twilight as preceding the full light of day; characterized by (as yet) imperfect enlightenment.
1679. T. Puller, Moder. Ch. Eng. (1843), 254. Proportionable to the first crepuscular and duskish light of those times.
1797. W. Taylor, in Monthly Rev., XXIV. 509. The favourable influence even of a partial and crepuscular day on the morals … and the happiness of the people.
1842. Motley, Lett. (1889), I. 96. The state of crepuscular civilization to which they have reached.
1852. Fraser’s Mag., XLVI. 679/2. That crepuscular period, when the historical sense was scarcely brought to a full state of activity.
3. Zool. Appearing or active in the twilight.
1826. Kirby & Sp., Entomol., xlix. (1828), IV. 525. Crepuscular insects.
1877. Coues & Allen, N. Amer. Rodentia, 653. Animals … of crepuscular or nocturnal habits.
