back-ordered
adjective
back-or·dered ˈbak-ˈȯr-dərd 
: ordered for purchase or delivery but not yet available : placed on back order
a list of back-ordered merchandise
The LX450 is back-ordered at many Lexus dealers.
Michael Shnayerson
Michael ShnayersonShe looked for generic brands of the medicine, but found they were back-ordered or unavailable for purchase. Kara Driscoll
Kara Driscoll
Word History
First Known Use
1901, in the meaning defined above