Definition of "crepuscular"

crepuscular

/kɹɪˈpʌs.kjʊ.lə/

adjective
comparative more crepuscular, superlative most crepuscular
1. Of or resembling twilight; dim.
2. (zoology) Active at or around dusk, dawn or twilight.
  Quotations
  That's why cats are crepuscular — most active at dawn and dusk — because mice and rats forage for food during these hours when fewer of their natural enemies are around.
  1999, J. Anne Helgren, Communicating with Your Cat‎, page 51