"Back order" means that a product is temporarily out of stock or not currently available, but can be ordered and delivered later when it becomes available again. Full definition
Also, that engine is on back order for about 3 weeks. (humblemechanic.com)
I can't see it doing better in the long term anywhere else (at least until my crystal ball comes in off of back order). (budgetsaresexy.com)
And that's why I'm putting all of the risk on my shoulders and backing your order with a 200 % money back guarantee. (secure.patriothealthalliance.com)