sit up
B1 neutral intransitive intransitive
In simple words
to sit straight up, or suddenly pay attention
Meanings
1 A2 neutral
to move from lying down or leaning back into an upright seated position
"She sat up in bed when she heard a noise downstairs."
"Harry sat up in bed and fumbled for his glasses."
— J.K. Rowling, Harry Potter series
Grammar: inseparable
2 B2
idiomatic
neutral
to become suddenly attentive, interested, or impressed
"Investors sat up when the company announced record profits."
"That made me sit up and take notice."
— Common public-interview wording; exact source not recalled
Grammar: inseparable
3 B1
idiomatic
neutral
to stay awake and out of bed later than usual, often for a reason
"The parents sat up waiting for their son to come home."
Grammar: inseparable
Usage notes
Common both literally and figuratively. The phrase 'sit up and take notice' is very frequent.
Commonly used with
in bed straight attention notice suddenly awake
Forms
Base
sit up
I/you/we/they
3rd person
sits up
he/she/it
Past simple
sat up
yesterday
Past participle
sat up
have + pp
-ing form
sitting up
continuous
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Synonyms
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