LSJ
Pass., with pf. and aor.2 Act., secede, revolt before, Th. 3.12, etc.
leave off or desist before, Pl. Smp. 175d, etc. ; μὴ π., πρὶν ἂν… Id. Phd. 85c; ἅπαντα… ἐξευρίσκεται, ἂν μὴ προαποστῇς Alex. 30.2.
depart from before, τῶν ὅπλων αποστῆναι, of soldiers laying down arms, D.C. 49.41.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)