1. (retailing definition) A part of an order that the vendor has not filled on time and that the vendor intends to ship as soon as the goods in question are received, manufactured, or procured. 2. (physical distribution definition) An order not filled or shipped at time originally requested and "kept on the books" to be shipped later.

Product ordered but out of stock and promised to ship when the product becomes available.

In supply chain terms when a customer order cannot be immediately fulfilled from stock, the customer requirement may be placed on ‘back order’.  This implies that a replenishment order will be raised [..]

An order for library materials that could not be filled when originally placed because at least one of the items requested was not in stock or was as yet unpublished. Back orders are held open for fut [..]

Out-of-stock items that cannot be shipped with a customer's original order and are sent to the customer as soon as available.

Product ordered but out of stock and promised to ship when the product becomes available. The process a company uses when a customer orders an item that is not in inventory; the company fills the orde [..]

is an order cannot be filled in the usual time expected.  

is an order that cannot be filled in the usual time expected.

The quantity of an item requisitioned by ordering activities that is not immediately available for issue but is recorded as a stock commitment for future issue.

That portion of an order that cannot be delivered at a scheduled time, but will be delivered at a later date when available. Also, to restock requested out-of-stock items.

A back order is an unfilled customer order. Back orders can be due to insufficient inventory level to fulfill an order, an order which is past due, or both.

Product ordered but out of stock and promised to ship when the product becomes available.