# shit in someone's Cheerios

idiom · Vulgar

Source: https://englishreference.com/idiom/shit-in-someones-cheerios
Updated: 2026-08-10

## Meaning

Synonym of piss in someone's cornflakes.

## Examples

- Don't let his bad mood shit in your Cheerios today.
- I was having a great morning until my boss started complaining and totally shit in my Cheerios.
- Even though the project was going well, the manager's sudden criticism seemed designed to shit in everyone's Cheerios.

## Origin

From the breakfast food Cheerios. The term comes from the notion that defecating in someone's Cheerios would ruin their day.

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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.