The Collaborative International Dictionary of English v.0.48:

Crepuscle \Cre*pus"cle\ (kr[-e]*p[u^]s"s'l), Crepuscule
\Cre*pus"cule\ (kr[-e]*p[u^]s"k[-u]l), n. [L. crepusculum, fr.
   creper dusky, dark: cf. F. cr['e]puscule.]
   Twilight. --Bailey.
   [1913 Webster] Crepuscular

WordNet (r) 3.0 (2006):

crepuscule
    n 1: the time of day immediately following sunset; "he loved the
         twilight"; "they finished before the fall of night" [syn:
         twilight, dusk, gloaming, gloam, nightfall,
         evenfall, fall, crepuscule, crepuscle]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "crepuscule":
   alpenglow, aurora, brown of dusk, brownness, candlelight,
   candlelighting, cocklight, dawnlight, dusk, duskingtide,
   first light, foredawn, gloam, gloaming, glooming, glow, half-light,
   morning twilight, owllight, the small hours, twilight