Definition of back up in US English:

back up

phrasal verb

  • 1(of vehicles) form a line due to congestion.

    ‘the traffic began to back up’
    • ‘Too many stoplights are a nuisance, backing up traffic, making people late, annoying everyone.’
    • ‘It is hoped this will combat problems resulting from the queue of taxis backing up into Kings Road.’
    • ‘He said traffic was continually backing up around Wood Street and Curzon Street.’
    • ‘Cars and other vehicles queued for hours to reach the fair, backing up through Stow Square and up to the Fosseway.’
    • ‘Traffic backed up on to Bradshawgate, Bolton, while he was treated at the scene.’
    • ‘Traffic was backing up as far as the motorways as roads in and around the city centre were closed by police.’
    • ‘It was dusk when he began directing traffic, which was backing up at a nearby intersection.’
    • ‘Diversions were set up along the A4 as traffic backed up to the Cross Keys Inn.’
    • ‘This can become so congested that at peak times that traffic can back up as far as the motorway.’
    • ‘Contractors are due to start work on January 13 to put in place a series of initiatives that they hope will help to ease congestion at locations where traffic constantly backs up.’
    • ‘On the odd occasion during peak times traffic backs up but it seems to be OK most of the time.’
    • ‘Traffic typically backs up in both the morning and evening rush hours, but drivers are reporting that the new road markings have made the delays much longer than normal.’
    • ‘As traffic backed up around the barricades, dozens of onlookers stared inside.’
    • ‘And when that traffic backs up, the result is employee downtime and increasing frustration.’
    • ‘Traffic on High Street wishing to turn left or right on to Church Street backs up due to the volume of vehicles at busy times.’
    • ‘The result at peak times is that the traffic stops, backs up on to Queen Street bridge and into Blossom Street.’
    • ‘Cars were parked across the road, and traffic was already beginning to back up.’
    • ‘Cars stop in the middle of the road to view wildlife, backing up traffic for miles.’
    • ‘Naturally, being an interstate highway and the only decent road in the state, there are lots of people to inspect, and the traffic backs up for several miles.’
    • ‘You see, you take away half of the road and the traffic backs up.’
  • 2(of running water) accumulate behind an obstruction.

    • ‘When the sewers become overwhelmed with rainwater the overflows work to ensure water is prevented from backing up in the system.’
    • ‘In earlier testimony, I likened this process to water backing up against a dam that is finally breached.’
    • ‘There is a limit to the amount of water the River Thames can take, without it backing up and flooding new areas.’
    • ‘It's caused by the onset of the dry season, when the water backed up in the Tonie Sap lake begins to drain into the Mekong.’
    • ‘The water began to back up and I had to seize a jug and begin bailing it out into the bath.’
    • ‘When the foul water sewer is overcharged, the foul water backs up and can force open the manhole cover in Mr. Marcic's front garden, thereby escaping into the garden.’
    • ‘As more and more water backed up, a temporary lake formed and grew larger and larger.’
    • ‘Often the water backs up because the drains are clogged.’