ἐπιτέμνειν

From LSJ

ποταμῷ γὰρ οὐκ ἔστιν ἐμβῆναι δὶς τῷ αὐτῷ → it is impossible to step twice in the same river, you cannot step twice into the same rivers

Source

Greek > English (Woodhouse Verbs Reversed)

(see also ἐπιτέμνω): cut, wound on the surface