un ‧ for ‧ giv ‧ a ‧ ble /ˌʌnfəˈɡɪvəb ə l◂ $ -fər-/ BrE AmE adjective
[ Word Family: verb : ↑ forgive ; noun : ↑ forgiveness ; adverb : ↑ unforgivably ; adjective : ↑ forgiving ≠ ↑ unforgiving ]
an unforgivable action is so bad or cruel that you cannot forgive the person who did it:
Patrick had deceived her, and that was unforgivable.
the unforgivable sin of informing on your friends
—unforgivably adverb