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.
(..) plight of any teacher have deserted I'm the one who I would be letting down wait (brought a letter from the teacher (Chivu Why? Doubled guard backup safety procedures prison may not be safe? questioning the security of prisons? both certainly Chevy) of the question, I'm just a messenger (..)2008 Kung Fu Panda