οἰστρηδόν
From LSJ
ψυχῆς πείρατα ἰὼν οὐκ ἂν ἐξεύροιο πᾶσαν ἐπιπορευόμενος ὁδόν· οὕτω βαθὺν λόγον ἔχει → one would never discover the limits of soul, should one traverse every road—so deep a measure does it possess
English (LSJ)
Adv.
A madly, Opp.H.4.142.
Greek (Liddell-Scott)
οἰστρηδόν: ἐπίρρ., μετὰ οἴστρου, ἐμμανῶς, Ὀππ. Ἁλ. 4. 142.