Hard Currency

What Does Hard Currency Mean?
A currency, usually from a highly industrialized country, that is widely accepted around the world as a form of payment for goods and services. A hard currency is expected to remain relatively stable through a short period of time, and to be highly liquid in the forex market.

Investopedia explains Hard Currency
Another criterion for a hard currency is that the currency must come from a politically and economically stable country. The U.S. dollar and the British pound are good examples of hard currencies.