ἐπιστραφής
From LSJ
αὐτὸν κέκρουκας τὸν βατῆρα τοῦ λόγου → you have struck the very threshold of the argument, you have struck the most important and chiefmost point
English (LSJ)
ές, A = ἐπιστρεφής, Ammon.Diff.p.54 V., Ptol.Asc. p.395 H.
German (Pape)
[Seite 985] ές, = ἐπιστρεφής, Ammon., l. d.