LSJ
ἡ, a sign from Zeus, an omen from the sky, esp. of thunder, lightning, rain, διοσημία ΄στί Ar. Ach. 171; pl., Stoic. 2.203, D.S. 2.19, Plu. 2.419e, Philostr. VA 2.33, Jul. Or. 7.212b. (Freq. written -εία in codd.)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)