An order to buy a security on a downtick or sell it on an uptick. It is a conditional order: the order is conditional upon the last price change. In other words, with this order, a trader can buy only on a downtick or zero – downtick (buy minus) and can sell only on an uptick or a zero – uptick (sell plus).

A trader will submit an order on down-tick when prices fall, and on up-tick when prices rise, usually accompanied with a limit order or stop order.