αἰφνίδιος

ον, ές, Adv.
A. unforeseen, sudden, A. Pr. 680, Th. 2.61, Arist. EN 1117a18; ἀφικνοῦνται αἰφνίδιοι τοῖς Χίοις Th. 8.14. Adv. ‐ίως Id. 2.53; also ‐ιον Plu. Num. 15. αἰφνιδιοτυχής, ές, profiting by strokes of good fortune, Vett. Val. 18.16.
Liddell, Scott & Jones
A Greek-English Lexicon, 1940
An open-access project