1 C1 informal
To become stiff or rigid, especially in the muscles or joints (non-standard variant of 'stiffen up').
"My knees always stiff up when the weather gets cold."
inseparable
stiff up
C1 informal inseparable intransitive
A non-standard or regional variant of 'stiffen up,' meaning to become stiff or rigid.
In plain English
To become hard and difficult to move, like your muscles after exercise.
What does "stiff up" mean?
One main meaning — here's how to use it.
Literal vs figurative
Words literally mean
To become stiff.
Actually means
To become hard and difficult to move, like your muscles after exercise.
Usage tip
This form is non-standard and uncommon. Most native speakers prefer 'stiffen up.' It may appear in informal speech in some dialects. ESL learners are advised to use 'stiffen up' instead.
Words that pair with "stiff up"
Natural word combinations native speakers use most often.
muscles joints back neck
How to conjugate "stiff up"
The five tense forms you'll use most often.
Base
stiff up
I/you/we/they
3rd person
stiffs up
he/she/it
Past simple
stiffed up
yesterday
Past participle
stiffed up
have + pp
-ing form
stiffing up
continuous
Hear "stiff up" in the wild
Listen to native speakers using "stiff up" in real YouTube videos — click a clip to watch it on Looplines.
Keep exploring
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