Definition of acronyctous in English:

acronyctous

adjective

Astronomy
rare

Origin

Mid 19th century; earliest use found in Joseph Thomas (1811–1891). From post-classical Latin acronyctus or its etymon Hellenistic Greek ἀκρόνυκτος rising at sunset, in opposition (from ancient Greek ἀκρο- + νυκτ-, νύξ: see nycti-) + -ous.

Pronunciation:

acronyctous

/ˌakrəˈnɪktəs/