Source : Webster's Revised Unabridged Dictionary (1913)

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.