Crossing stock is the pairing off of two offsetting customer orders by the same floor broker. The floor broker executing the cross must first show the order to the crowd for possible price improvement before crossing the orders.
Applying "Crossing Stock" to Securities Exams:
At times when a floor broker has two offsetting orders for the same security the broker may try to cross those orders. If a floor broker had 5000 shares of XYZ to buy for a customer and 5000 shares of XYZ to sell for another customer the floor broker may walk over to the trading post and announce the orders and execute the orders against one another. The cross must take place at a price that does not favor either order.