Broadly, crepuscular is an adjective that describes something of or relating to twilight (dawn or dusk). In a zoological sense it refers to animals that are active in the twilight, such as skunks, fireflies, and deer.
Crepuscular is a direct match to the Latin crepusculum, meaning twilight, with the English -ar suffix to replace the -um.
Dazzle your date with the right word for the moment the next time you're out for a sunset stroll. Crep-US-cue-ler. You've totally got this.
–C