English to English

adjective (a)

• not suitable to be exchanged(adj.all)

  Antonym:
  exchangeable
  

  source: wordnet30
• used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value(adj.all)

  Synonym:
  inconvertible, unconvertible
  Antonym:
  convertible, exchangeable
  

  source: wordnet30