Forex is a common abbreviation for Foreign Exchange - money from other countries, and the act of changing money from one currency to another at the current exchange rate. This can be the few dollars, Euro or other funny money in cash or traveller's checks that you need before going on holiday, larger bank transfers, or the trading on the international financial markets.

Forex was not noded until now on 6 January 2005, but as a Google search term, "forex" gets over 8 million results today. That's a real word if anything is.