noun, plural eu·ros, eu·ro.
( sometimes initial capital letter ) the official common currency of 17 European Union nations (Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia, and Spain). It is also the official currency of Andorra, Kosovo, Monaco, Montenegro, San Marino, and the Vatican City. In 1999 the euro was first adopted by 11 nations as an alternative currency in noncash transactions. Then in 2002 the euro fully replaced existing currencies in 12 European Union nations, before being adopted more widely. Symbol: €