sit up

sit up idiom
  1. Rise to a sitting position from lying down, as in The sick child sat up and asked for a drink of water. [Early 1200s]
  2. Stay up later than usual, as in The nurse sat up with her all night long. [Mid-1500s]
  3. Sit with the spine erect, as in She was always telling the students to sit up. [Early 1700s]
  4. Become suddenly alert, as in The students sat up when he brought up the test. The same sense appears in the related sit up and take notice, as in When he mentioned the arrival of a movie star, they all sat up and took notice. [Late 1800s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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