How does taking ἀντιτείχισμα here as "buttressing" or "buttressing wall" sound?Thucydides, [i]The Peloponnesian War[/i], 2.77 wrote:μετὰ δὲ τοῦτο οἱ Πελοποννήσιοι, ὡς αἵ τε μηχαναὶ οὐδὲν ὠφέλουν καὶ τῷ χώματι τὸ ἀντιτείχισμα ἐγίγνετο, νομίσαντες ἄπορον εἶναι ἀπὸ τῶν παρόντων δεινῶν ἑλεῖν τὴν πόλιν πρὸς τὴν περιτείχισιν παρεσκευάζοντο.
After this the Peloponnesians, finding that their engines effected nothing, and that their mound was met by the counter-work, concluded that their present means of offence were unequal to the taking of the city, and prepared for its circumvallation.
My thinking is like this... The earthworks that they had thrown up were not right round the city, but in places, presumably with the engines of war behind or near them. At those points, the citizens of the town buttressed the city walls. So, what had originally been chose as points of weakest defence, became strong enough to withstand attacks. Etymologically, the ἀντι- of ἀντιτείχισμα might seem too go with the χῶμα, but I think it is a fixed part of the meaning of the word ἀντιτείχισμα "something placed against the wall", not "a wall over against the χῶμα (or whatever else is mentioned in a passage)". There was a gap between the earthworks and the city wall (τεῖχος).
On the other hand, Procopius, Buildings (Προκοπίου, Περὶ κτισμάτων) II, III describes a different kind of work using the word ἀντιτείχισμα - a kind of intermediary line of defence.
A commentary on the Greek in Modern Greek by Christo Papanastasiou explains the situation as τὸ μηνοειδὲς τεῖχος. Presumably he has read that straight from Procopius into Thucydides. In the Thucydidean story, however, there doesn't seem to have been preparatory work and the distance between the wall and the earthwork seems to have been small.
Modern Greek definitions are given in different contexts as
Live-pedia wrote:τετράγωνος κίονας που είναι στερεά κατασκευασμένος και που χρησιμεύει για να στηρίζει μιαν αψιδωτή αντηρίδα ενός κτιρίου.
Neither of which refer to a second wall separated from the first, but rather in terms of it providing some support to another structure.Λεξικό της κοινής νεοελληνικής wrote:τείχος που στηρίζεται σε άλλο τείχος για να το ενισχύει.