I.unspoken, unsaid, Lat. indictus, Od., etc.; οὐκ ἐπ᾽ ἀρρήτοις λόγοις not without warning spoken, Soph.
II.not to be spoken, not to be divulged, of sacred mysteries, Hdt., Eur., etc.; διδακτά τε ἄρρητά τ᾽, i. e. things profane and sacred, Soph.
2.unutterable, inexpressible, horrible, Lat. nefandus, id=Soph., Eur.; ἄρρητ᾽ ἀρρήτων "deeds without a name, " Soph.
III.in Mathem., ἄρρητα, irrational quantities, surds, Plat.