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.
(..) They naused up the mainframe. Naused it up! -You understand him? -I'll explain later. They' re so pony they blew the backup grids one by one. Basher, what happened? They did what I would have done but by accident. Now they know their weakness, they're fixing it. (..)2001 Ocean's Eleven