ἔρεισις
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)
εως, ἡ,
A propping up, shoring up, οἰκίας BCH35.243(Delos, ii B.C.). 2 resting, supporting, ἡ ἐπ' ἐδάφους ἔ. τοῦ ποδός Aristeas 69. 3 pushing against, thrusting, τοῦ πέτρου D.H.Comp.20 ; τοῦ χείλους Ath.11.488e. 4 leverage, Menesth. ap. Erot. s.v. ἄμβην.
German (Pape)
[Seite 1024] ἡ, das Stützen, Anstämmen, Entgegenstämmen, D. Hal. u. a. Sp.
Greek (Liddell-Scott)
ἔρεισις: -εως, ἡ, ἡ μετὰ δυνάμεως ὤθησις, τὴν τοῦ πέτρου ἔρεισιν, περὶ τῆς μεγάλης πέτρας ἣν ὤθει πρὸς τὰ ἄνω μετὰ πολλοῦ κόπου ὁ Σίσυφος, Διον. Ἁλ. περὶ Συνθ. 20 στήριξις, τοῦ χείλους Ἀθην. 488Ε.