- inconvertible, unconvertible, unexchangeable - used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value
Antonyms: convertible, exchangeable, cashable, redeemable
- inconvertible, untransmutable - not capable of being changed into something else; "the alchemists were unable to accept the inconvertible nature of elemental metals"
Antonym: commutable (indirect, via incommutable)