ATBEST ORDER

at-best order: translation

An order submitted to the order book with a specified size which may execute, either in part or in its entirety, against eligible orders at the price of those orders with any unexecuted portion being rejected from the book. Exchange Handbook Glossary

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An order submitted to an order book to deal in a specified number of shares. It may execute, either in part or in full, against eligible orders (at the price of those orders). Unexecuted portions of at best orders are rejected from the order book. Sometimes referred to as an 'Aggressive Type A' order. London Stock Exchange Glossary