IPA: //ʌnˈhjuːn//
KK: /ʌnˈhjun/
Not shaped or finished; in a rough or natural state.
The unhewn stone was left in its natural form, ready to be carved later.
Unhewn → It is formed from "un-" (meaning not) and "hewn" (from Old English "hiwian", meaning to cut or shape). The word "unhewn" means not cut or shaped, referring to something in its natural state.
Think of something that is 'not' ('un-') 'cut or shaped' ('hewn') — that's why unhewn describes something in its natural form.