Wordnet 3.0
NOUN (2)
1. 
 a currency that is not likely to depreciate suddenly in value; 
- Example: "the countries agreed to conduct their bilateral trade in hard currency, replacing previous barter arrangements"- Example: "Germany once had a solid economy, good fiscal and monetary policies, and a hard currency"2. 
 money in the form of bills or coins; 
- Example: "there is a desperate shortage of hard cash"[syn: cash, hard cash, hard currency]
WordNet (r) 3.0 (2006):
hard currency
    n 1: a currency that is not likely to depreciate suddenly in
         value; "the countries agreed to conduct their bilateral
         trade in hard currency, replacing previous barter
         arrangements"; "Germany once had a solid economy, good
         fiscal and monetary policies, and a hard currency"
    2: money in the form of bills or coins; "there is a desperate
       shortage of hard cash" [syn: cash, hard cash, hard
       currency]