1 B1 neutral
Of a glass surface, to become covered in condensation so that it is difficult or impossible to see through.
"My glasses fogged up the moment I walked into the warm kitchen from the cold."
inseparable
fog up
B1 neutral separable transitive/intransitive
To become covered in a thin layer of condensation or mist that obscures visibility.
In plain English
Get covered in mist or steam so you can't see through it — like glasses or a car windscreen.
What does "fog up" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 B1 neutral
To cause a surface to become obscured with condensation or mist.
"The hot shower fogged up the bathroom mirror completely."
separable
Literal vs figurative
Words literally mean
To become covered in fog or a fog-like substance — fully transparent.
Actually means
Get covered in mist or steam so you can't see through it — like glasses or a car windscreen.
Usage tip
Most commonly used for glasses, mirrors, car windscreens, and windows. Very frequent in everyday British English. Can be intransitive ('my glasses fogged up') or transitive ('the steam fogged up the mirror'). American English more often uses 'fog up' or 'steam up' interchangeably.
Words that pair with "fog up"
Natural word combinations native speakers use most often.
glasses windscreen windshield mirror visor windows lens
How to conjugate "fog up"
The five tense forms you'll use most often.
Base
fog up
I/you/we/they
3rd person
fogs up
he/she/it
Past simple
foged up
yesterday
Past participle
foged up
have + pp
-ing form
foging up
continuous
Hear "fog up" in the wild
Listen to native speakers using "fog up" in real YouTube videos — click a clip to watch it on Looplines.
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