unpardonable

un- +‎ pardonable

unpardonable (comparative more unpardonable, superlative most unpardonable)

1. impossible to pardon; impossible to excuse or justify
   • 1900, Gilbert Parker, An Unpardonable Liar:

     "I can understand your being wicked," she said keenly, "but not your being cowardly. That is and was unpardonable."

   • 1912, Ralph Connor, Corporal Cameron of the Northwest Mounted Police:

     To lose a game was bad enough, but to round on a comrade was unpardonable; while to lose from the game a half-back of Cameron's calibre was unthinkable.

• inexcusable, unforgivable, unremittable
• unjustifiable, indefensible

• pardonable

• unpardonable sin

• pardonable

• unpardonable in An American Dictionary of the English Language, by Noah Webster, 1828.