Wash Trade
A matched deal which produces neither a gain nor a loss.

Whipsaw
Term for where a trader takes a position, then has to move against it triggering stop loss limits and liquidation of positions, then having to move in the original direction. Normally occurs in volatile markets.

Working Day
A day on which the banks in a currency's principal financial center are open for business. For FX transactions, a working day only occurs if the bank in both financial centers are open for business (all relevant currency centers in the case of a cross are open).