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back up - definition and synonyms


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90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.



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phrasal verb
Word Forms
present tense
I/you/we/theyback up
he/she/itbacks up
present participlebacking up
past tensebacked up
past participlebacked up
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  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.

    Traffic is backing up on all routes out of town.

    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 backward a short distance

    I need everyone to back up about 10 steps.

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

    See if you can back up a little farther.

    back something up something:

    I’ll back the car up the driveway.

  7. 7
    [intransitive] 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

sea lion

in an online conversation, repeatedly asking a person questions which suggest that you are interested in what they are talking about, but are actually intended to annoy them

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an electric skateboard

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