# one's back is up

idiom

Source: https://englishreference.com/idiom/ones-back-is-up
Updated: 2026-08-10

## Meaning

One is offended or angry.

## Examples

- His back is up because you criticized his work.
- I tried to offer some helpful advice, but her back was up immediately and she refused to listen.
- The politician's back was up after the journalist questioned his integrity, leading to a heated and defensive response during the live interview.

## Origin

From the physical habit of an angry cat, which arches its back when it finds a situation disagreeable. The idiom records the feline tendency to raise the spine as a defensive posture before an altercation.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.