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.
(..) I'm talking about that briefcase being locked in your desk. Yeah, I saw it. And I know what it is. It's your backup plan in case this doesn't work out. You can make some quick cash and go right back to the life you told me (..)2011 TvShow: Suits Title: Pilot Season: 1 Episode 1