Eurodollars are time deposits denominated in U.S. dollars at banks outside the United States, and thus are not under the jurisdiction of the Federal Reserve. Consequently, such deposits are subject to much less regulation than similar deposits within the U.S. The term was originally coined for U.S. dollars in European banks, but it expanded over the years to its present definition. A U.S. dollar-denominated deposit in Tokyo or Beijing would be likewise deemed a Eurodollar deposit. There is no connection with the euro currency or the eurozone.
More generally, the euro- prefix can be used to indicate any currency held in a country where it is not the official currency: for example, Euroyen or even Euroeuro.