A currency cross — or cross-rate — is a pair that does not involve the US dollar, such as EUR/GBP, EUR/JPY, or GBP/JPY. The name dates from when most exchange rates were quoted against the dollar, so deriving the rate between two non-dollar currencies meant 'crossing' through the dollar.
Today crosses trade directly and deeply, but the concept remains useful: a cross isolates the relationship between two currencies without dollar influence muddying the picture.
Why trade crosses
Crosses let traders express a focused view. If you think the euro will outperform the pound specifically — regardless of what the dollar does — EUR/GBP is a cleaner expression than taking opposing positions in EUR/USD and GBP/USD. Crosses can also offer trends and volatility profiles different from the dollar majors.
Yen crosses such as EUR/JPY and GBP/JPY are widely watched as risk-sentiment barometers, because the yen's safe-haven behaviour shows through clearly when the dollar is stripped out.