What is the meaning of the word "hard currency"?

Definitions:

  1. a currency that is not likely to depreciate suddenly in value copy to clipboard noun
    • The countries agreed to conduct their bilateral trade in hard currency, replacing previous barter arrangements. copy to clipboard
  2. money in the form of bills or coins copy to clipboard noun
    • We need to get some hard currency since this restaurant does not accept cards. copy to clipboard

Synonyms: