ἐπημοιβός
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)
όν, late ή, όν Opp.H.5.135:—
A crossing, ὀχῆες ἐ. (unless = shifting to and fro) Il.12.456; τελαμῶνες ἐ. cross-belts, Opp.C. 1.98. 2 alternating, serving for change, χιτῶνες ἐ. Od.14.513; ἀστέρες Arat.190; πρηδόνες Nic.Th.365.