unimpairable

From un- +‎ impairable.

unimpairable (comparative more unimpairable, superlative most unimpairable)

1. That can not be impaired.
   • 1662, Henry More, The Defence of the Moral Cabbala:

     this Metaphysical Earth […] being the lowest degree and shadow of Being; and not only immovable, but undiminishable and unimpairable, as I have already noted .

• “unimpairable”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.