sit up

1. 1.

   not go to bed

   “Don't stay up so late--you have to go to work tomorrow”

   “We sat up all night to watch the election”

   Synonymsstay up

   Broaderwake
2. 2.

   change to an upright sitting position

   “He sat up in bed”

   Broaderchange posture

Questions about sit up

What does sit up mean?

sit up means "not go to bed". That is the primary sense; the word has 2 in total, listed in full on this page.