sit up

sit up

1. To rise up to a sitting position after having been lying down. I woke up very thirsty, so I sat up to take a drink of water.
2. To raise someone up into a sitting position after they have been lying down. In this usage, a noun or pronoun is used between "sit" and "up." They sat the patient up so she could see her visitors.
3. To sit with a fixed, upright posture. Please sit up during class—stop slouching at your desk like that!
4. To suddenly take notice of something or become very alert. Our son sat up the moment we mentioned the possibility of going to Disneyland.
See also: sit, up
Farlex Dictionary of Idioms.

sit up

 
1. to rise from a lying to a sitting position. When the alarm went off, he sat up and put his feet on the floor. She couldn't sleep, so she sat up and read a book.
2. to sit more straight in one's seat; to hold one's posture more upright while seated. Please sit up. Don't slouch! You wouldn't get backaches if you would sit up.
See also: sit, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

sit up

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]
See also: sit, up
The American Heritage® Dictionary of Idioms by Christine Ammer.

sit up (and take notice)

suddenly start paying attention or have your interest aroused. informal
See also: sit, up
Farlex Partner Idioms Dictionary

sit up

v.
1. To rise from lying down to a sitting position: The patient sat up for her meal.
2. To sit with the spine erect: The nanny told the children to sit up.
3. To stay up later than the customary bedtime: My parents sat up waiting for me to come home.
4. To become suddenly alert: The students sat up when the teacher mentioned the test.
See also: sit, up
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • give with
  • give with (something)
  • give with something
  • thirsty for
  • thirsty for (someone or something)
  • thirsty soul
  • (one's) tongue is hanging out
  • someone's tongue is hanging out
  • poise over
  • poise over (someone or something)
References in periodicals archive
The events include 3.2 kilometer run, pull ups, sit ups, push ups, and combat efficiency test followed by closing and prize distribution ceremony.
While Sapper Akmal Hussain did 2134 Sit Ups to secure 1st Position in this event.
Many short bursts of activity can be an effective alternative to prolonged periods of exercise, so while enjoying your favourite TV show, why not perform 10 press ups and sit ups during each ad break?
With our re-tests (a shuttle run and a test to see how many press ups and sit ups we can do in a two minute period) looming, we have everything to gain and nothing to lose.
An inexpensive dumbbell set and enough room to do push ups and sit ups are all you need for a good strength-building routine.
Sapper Akmal Hussain did 2,134 Sit Ups to secure 1st Position in this event.
Paddy, who moved to Balsall Common from Sheldon almost four years ago, is training hard for the challenges with a gruelling fitness regime, which sees him running five miles, rowing 10,000m, cycling five miles, completing 500 press ups and 500 sit ups, six days a week.
"doing sit ups with your knees bent will isolate your tummy muscles more, and protect your back.