Webster’s Revised Unabridged Dictionary · 1913
Crepuscular
Cre·pus′cu·lar (-k?-l?r), Cre·pus′cu·lous (-l?s), a. [Cf. F. crépusculaire.] 1. Pertaining to twilight; glimmering; hence, imperfectly clear or luminous.
This semihistorical and crepuscular period. Sir G. C. Lewis.
2. (Zoöl.) Flying in the twilight or evening, or before sunrise; — said certain birds and insects.
Others feed only in the twilight, as bats and owls, and are called crepuscular. Whewell.