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 going to go hard after them, Dennis. And have them in bracelets within a month. Hey, Vallon I'm locking up right now. Camera's off? Clear. You were right, we should've had backup. I'm sorry. You're not really sleeping are you? Asshole. Sergeant, "Thomas Ryan," NYPD, (..)2014 RoboCop
(..) Nothing. How do you think that happened? I tell you Murphy this is a mistake. These guys will shoot you just to see if they gun work. We need backup. We call for backup words going to get around the station. And he's going to disappear. It's gonna be alright. We told Vallon we were gun (..)2014 RoboCop