διηέριος
From LSJ
εἰς πέλαγος σπέρµα βαλεῖν καὶ γράµµατα γράψαι ἀµφότερος µόχθος τε κενὸς καὶ πρᾶξις ἄκαρπος → throwing seeds and writing letters at sea are both a vain and fruitless endeavor
English (LSJ)
α, ον, also ος, ον,
A through the air, δ. ποτέονται A.R.2.227, etc.:—in Prose, διᾱέριος, ον, Luc.Salt.42, etc.; διαέρια λέγειν, = μετέωρα λ., Id.Icar.1.
