Of or resembling twilight; dim. / (zoology) Active at or around dusk, dawn or twilight.

The quality of being crepuscular.

plural of crepuscularity

A sunbeam seen just after sunset or just before sunrise, caused by a cloud below the horizon and dust particles in the air above the horizon. / A cloud shadow cast on the bright sky.

plural of crepuscular ray

In a crepuscular way; dimly; indistinctly.