Abbott-Smith Manual Greek Lexicon
ἄρρητος (G731)
1 ** ἄρρητος , -ον ( ἀ- neg., ῥητός , ῥέω ), [in Sm.: Le 18:23 *;] unspoken (Hom., al.). unspeakable (Hat., al.; freq. in Inscr.; MM, s.v.): II Co 12:4 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain