An order instruction specifying that a trade should be executed at a given price or at a more favorable one. A buy order executes at the specified price or lower; a sell order at that price or higher. This instruction gives the broker flexibility to fill at improved prices while ensuring the trader never receives a worse fill than what was specified.
Example
“I submitted a buy order at or better than $50.00, and it filled at $49.85 due to a momentary dip in the ask.”