1 B1 idiomatic informal
To make a serious mistake that ruins or disrupts a plan, operation, or situation.
"Someone fouled up the bookings and now there aren't enough rooms for everyone."
separable
foul up
B1 informal separable transitive/intransitive
To ruin, spoil, or make a serious mess of something through mistakes or incompetence.
In plain English
Make a big, serious mistake that ruins or confuses something.
What does "foul up" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B2 neutral
To become blocked, tangled, or confused (often of machinery or a system).
"The whole production line fouled up when the conveyor belt jammed."
inseparable
Usage tip
Originally from military slang. A polite alternative to stronger expletive expressions. 'Foul-up' (noun) is the corresponding noun form. Common in both American and British English.
Words that pair with "foul up"
Natural word combinations native speakers use most often.
plan operation schedule deal mission situation
How to conjugate "foul up"
The five tense forms you'll use most often.
Base
foul up
I/you/we/they
3rd person
fouls up
he/she/it
Past simple
fouled up
yesterday
Past participle
fouled up
have + pp
-ing form
fouling up
continuous
Hear "foul up" in the wild
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