Cross the spread
Crossing the spread occurs when a trader (or algorithm) is forced to buy at the offer price or sell at the bid, instead of letting, for instance, the buy limit order rest at the bid and letting the market cross.

Crossing the spread occurs when a trader (or algorithm) is forced to buy at the offer price or sell at the bid, instead of letting, for instance, the buy limit order rest at the bid and letting the market cross.