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.
(..) - Clawhauser! Clawhauser, listen to me. We have a -! Jaguar gone savage! - In Tu-junga! - It's Tu-hunga! Okay, we're sending backup. There! Head to the sky-trans! Get in. Carrots? Carrots! Go! Buddy, one predator to another... Now I can tell you're a little tense, (..)2016 Zootopia