ἀκρόνυκτος

ον, Subst., ἡ
A. rising at sunset: hence, in opposition, Ζεύς Vett. Val.168.13; ἀ. σχηματισμοί, προηγήσεις, Ptol. Alm. 10.6, Tetr. 78:—as Subst., ‐νυκτος,ἡ, with or without φάσις, opposition, Ptol. Alm. 10.7, Tetr. 77. (Freq. written ἀκρων‐.)
Liddell, Scott & Jones
A Greek-English Lexicon, 1940
An open-access project