1 : of, relating to, or resembling twilight : dim
2 : active in the twilight
“The whisper of his conviction seemed to open before me a vast and uncertain expanse, as of a crepuscular horizon on a plain at dawn….” (Joseph Conrad, Lord Jim)
Did you know?
The early Romans had two words for “twilight.” “Crepusculum” was favored by Roman writers for the half-light of evening, just after the sun sets; it is a diminutive formation based on their word for “dusky,” which is “creper.” “Diluculum” was reserved for morning twilight, just before the sun rises — it is related to “lucidus,” meaning “bright.” We didn’t embrace either of these Latin nouns as substitutes for our Middle English “twilight,” but we did form the adjective “crepuscular” in the 17th century. At first, it only meant “dim” or “indistinct,” often used in a figurative sense. In the 1820s, we added its special zoological sense, describing animals that are most active at twilight.