Definition of back order in English:

back order

noun

  • A retailer's order for a product that is temporarily out of stock with the supplier.

    ‘the phone I wanted was on back order’

verb

[with object]
  • Place an order for (a product) that is temporarily out of stock.

    ‘the item was back-ordered by our distributor’
    ‘the taps can be back-ordered and take up to three months for delivery’