back up

back· up

back up

v. i.
  1. to move in a reverse direction; -- used of vehicles or animals.
  2. to accumulate due to a blockage of flow; as, a traffic backup due to an accident; a sewage backup.

back up

v. t.
  1. to serve as a backup{3} for (another person or persons); as, the patrolmen backed up the detectives as they went inside to make the arrest; the center fielder backed up the shortstop on the play.
  2. to make a backup{5} of; as, the sysop backed up the purchasing data files every night. (Computers)