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.
(..) We never really die. Sorry, sir, I don't agree... I'm fine, fine. I'm going to tell them to stop following us. Don't bother. Hey, I got you backup... Give me the case. Kill her and get the pouch. Don't stand there, kill her! Open it. Let's go. (..)2014 Lucy