unspeakable
From LSJ
σιγᾶν ἄμεινον ἢ λαλεῖν ἃ μὴ πρέπει → it's better to keep silence than to say what's not appropriate (Menander)
English > Greek (Woodhouse)
adjective
P. and V. ἄρρητος, ἀπόρρητος, P. ἀμύθητος, V. ἄφραστος, ἄγρυκτος, ἀναύδητος, ἀνεκλάλητος, ἄλεκτος, δύσφατος, ἄσπετος, ἀφώνητος, ἀναυδής, ἄεπτος, ἀνέκφραστος, ἀθέσφατος, ἀπειρέσιος, ἄλαλος, ἀνεκφώνητος, ἄφθεγκτος, ἄφατος, ἀπόφημος, ἄναυδος, ἀλάλητος.
indescribable: P. ἀμύθητος, P. and V. κρείσσων λόγου, Ar. οὐ φατός, Ar. and V. ἀνωνόμαστος.
extraordinary: P. and V. ἀμήχανος.