noun

• (computing) A copy of a file or record, stored separately from the original, that can be used to recover the original if it is damaged or destroyed.
  "After the power failure, we had to restore the database from backup."
• (law enforcement) Reinforcements.
  "He's got a gun! You'd better send for backup."
• (music) Accompaniment.
  "Debbie Ahn, on piano, provided some mesmerizing back-up and many fiery, on-target solos."

adj

• (computing) That is intended as a backup.
  "Make a backup copy of that file."

verb

• (computing, nonstandard) Alternative form of back up.
  "We have two methods for backupping: the first one is writing the contents of disks onto magnetic tapes and the other is making a copy of the contents of disks on the disk of the mainframe computers of the laboratory."