(computer science) a copy of a file or directory on a separate storage device; "he made a backup in case the original was accidentally damaged or erased"
an accumulation caused by clogging or a stoppage; "a traffic backup on the main street"; "he discovered a backup in the toilet"
breed animals or plants using parents of different races and varieties; "cross a horse and a donkey"; "Mendel tried crossbreeding"; "these species do not interbreed"