The policeman called for 'backup' [=called for other police to come and help him] because the suspect was carrying a gun.
There was a traffic 'backup' [=('Brit') 'tailback'] for miles on the road because of the accident.
His role on the team is to be a 'backup' to the regular quarterback.
(..) Where's everyone going? We got a new home to build. Come on. I'll tell you about the time I took on an army of Manhunters... ...and my only backup was this squirrel. (..)2011 Green Lantern: Emerald Knights