Barter is a simple form of trade where goods or services are exchanged for a certain amount of other goods or services, i.e. there is no money involved in the transaction. Barter trade was common in societies where no monetary system existed or in economies suffering from a very unstable currency (as when hyperinflation hits) or a lack of currency.
In finance, the word "barter" is used when two corporations trade with each other using non-money financial assets (such as U.S. Treasury bills). Alternatively, the standard definitions of money could be seen as being too narrow and needing to be expanded to increase near-money assets.