What is the meaning of All or none order (AON)?

All or none order (AON) is used in context of general equities. A limited price order that is to be executed in its entirety or not at all (no partial transaction), and thus is testing the strength/conviction of the counterparty. Unlike an FOK order, an AON order is not to be treated as cancelled if not executed as soon as it is represented in the trading crowd, but instead remains alive until executed or cancelled. The making of "all or none" bids or offers in stocks is prohibited, and the making of "all or none" bids or offers in bonds is subject to the restrictions of Rule 61. AON orders are not shown on the specialist's book because they cannot be traded in pieces. Antithesis of any-part-of order. See: FOK order.