'At or better' is an order to deal at a specific rate or better.
The balance of trade is the value of a country's exports minus its imports.
Ballooning is the practice by market makers of increasing pip spreads during fast or illiquid markets.
A Forex bear market is a Forex market distinguished by declining prices.
A centralized market is any market where all orders are routed to one central exchange. The Forex market is not a centralized market.
The cash market is the market in the actual financial instrument on which a futures or options contract is based.
The cable is Forex trader jargon referring to the Sterling/USD exchange rate. The cable is so called because the rate was originally transmitted via a transatlantic cable beginning in the mid-1800's.
The Bundesbank is Germany's central bank.
A Forex bull market is a Forex market distinguished by rising prices.
In a professional trading environment, a book is the summary of a trader's or desk's total positions.