Buy Minus Order
An order to buy a security with very specific price requirements. The price at which the order is executed may not be higher than the security's last price if the last price was a downtick or a zero-minus tick. If the previous trade was an uptick or a zero-plus tick, the price may not be higher than the difference between the last price and its change (which is itself the difference between the current price and the close on the previous trading day).
Of or relating to an order to purchase a security only when the last change in the security's price is downward. A buy-minus order may be used to acquire a position in a security during a short-term price decline.