back up - definition and synonyms

phrasal verb
present tense
I/you/we/theyback up
he/she/itbacks up
present participlebacking up
past tensebacked up
past participlebacked up
  1. 1
    [transitive] back someone up to give support to someone by telling other people that you agree with them

    If I ask for more money will you back me up?

  2. 2
    [transitive] to show that an explanation or belief is probably true

    All the evidence backs up her story.

  3. 3
    [intransitive/transitive] to make a copy of information on your computer
  4. 4
    [intransitive/transitive] if traffic backs up, or if it is backed up, the vehicles are in a long line and waiting to continue moving

    Cars were backed up for miles.

    1. a.
      if a toilet, sink, or drain backs up, or if it is backed up, water cannot flow through it because something is blocking it
    2. b.
      if a system backs up, or if it is backed up, it has slowed down or stopped working because there is too much of something for it to deal with

      Orders are really backed up this month.

  5. 5
    [intransitive] to move backwards a short distance

    I need everyone to back up about 10 paces.

  6. 6
    [intransitive/transitive] to make a car go backwards

    See if you can back up a bit further.

    back something up something:

    I’ll back the car up the driveway.

  7. 7
    [intransitive] mainly American used for telling someone to return to something that was said earlier

    Back up: didn’t you say they had already met?

See also main entry: back