that which flows, a river, stream, ποταμοῖο ῥέεθρα the streams, waters of . ., Il. 14.245; ἐρατεινὰ ῥ. 21.218; Στυγὸς ὕδατος αἰπὰ ῥ. 8.369, cf. h.Hom. 19.9, etc.; παρθενόσφαγα ῥ. streams of a maidenʼs blood, A. Ag. 210 (lyr.): sg., ἐκτρέψασα τοῦ ποταμοῦ τὸ ῥέεθρον πᾶν ἐς τὸ ὤρυξε χωρίον Hdt. 1.186, cf. 179, Th. 7.74; Ἀλφεοῦ ῥέεθρον Pi. O. 9.18; ῥέεθρον ἁγνοῦ Στρυμόνος A. Pers. 497; ὅταν περάσῃς ῥεῖθρον Id. Pr. 790; esp. of rivulets, brooks, X. Cyn. 5.15, Plb. 3.71.4, Jul. Or. 3.126d.
bed or channel of a river, ἄψορρον . . κῦμα κατέσσυτο καλὰ ῥέεθρα Il. 21.382; ποταμοῦ ῥ. ἀπεξηρασμένον Hdt. 7.109; ποταμὸν ἐκτραπέσθαι ἐκ τῶν ἀρχαίων ῥ. Id. 1.75; παρατρέψας [τὸν ποταμὸν] διʼ ὧν νῦν ῥέει ῥεέθρων, i.e. ἐκ τῶν ῥεέθρων διʼ ὧν νῦν ῥέει, Id. 7.130, cf. 127:—signf. I and ΙΙ are sts. hard to distinguish, cf. Hdt. 1.191, 2.11, 9.51.