The Greek adjective arrhētos (from a- privative + rhētos, spoken) means 'unutterable,' 'inexpressible,' or 'unspeakable' — referring to something that cannot or should not be spoken, whether because human language is insufficient or because the content is too sacred for ordinary speech.
Paul uses arrhētos in 2 Corinthians 12:4 to describe what he heard during his extraordinary experience of being caught up to the third heaven: 'he heard inexpressible things, things that no one is permitted to tell.' The content of Paul's vision was not merely difficult to describe — it was categorically beyond verbal communication. This reminds believers that God's reality infinitely exceeds human capacity to capture or convey it, preserving a sanctifying sense of holy mystery in the faith. The deepest encounters with God leave us speechless — and that silence is itself a form of worship.