Synonyms: inconvertible, unconvertible, unexchangeable
Definition: used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value
Similar words: irredeemable
Definition: (of paper money) not convertible into coin at the pleasure of the holder
Synonyms: unexchangeable
Definition: not suitable to be exchanged
Similar words: incommutable
Definition: not interchangeable or able to substitute one for another
Usage: a rare incommutable skill