# foul up

CEFR B2 · Phrasal verb

Source: https://englishreference.com/word/foul-up
Updated: 2026-10-22

## Definition

to spoil something or make a mistake that causes a plan to go wrong. You use this when you have accidentally made a mess of a situation.

For teachers: To bungle or spoil a task, situation, or arrangement through error or incompetence. The verb is often used transitively with a direct object, though it can also function intransitively to describe a general failure.

## Examples

- I really fouled up my job interview this morning.
- The travel agency fouled up our hotel reservation, so we had to find a new place to stay at midnight.
- A single miscalculation in the logistics chain can foul up the entire distribution network for weeks.

## Pitfalls

- Not "The error fouled up of the system." but "The error fouled up the system." — The verb is transitive and does not require the preposition 'of' before the object.

## Usage notes

- The phrase is informal and can be used with or without a direct object.
- Teaching tip: Compare with 'mess up' or 'screw up'; 'foul up' is slightly less common in modern youth slang but remains a standard informal choice for describing errors.

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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.