Crepuscular \Cre*pus"cu*lar\ (-k?-l?r), Crepusculous \Cre*pus"cu*lous\ (-l?s), a. [Cf. F. cr['e]pusculaire.] 1. Pertaining to twilight; glimmering; hence, imperfectly clear or luminous. This semihistorical and crepuscular period. --Sir G. C. Lewis. 2. (Zo["o]l.) 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.