Cutting something out can mean removing or deleting something. For example, if you are writing an essay and you don't like one paragraph in your essay, you can cut out that section or cut that section out. People who make movies often cut some parts out when they are putting the film together.
However, there's another meaning to cutting it out that I want you to learn. It is more idiomatic; it means to stop doing something right away. We often say this to friends or family when we are upset or annoyed and we want them to stop what they are doing immediately.
When someone's teasing you about your new haircut and you're tired of it, you can say, "Cut it out!" If you're
watching your friend's kids and they are fighting instead of eating their dinner, you can sternly say, "Guys, cut it out or there will be no dessert."
We can also use cut it out in a friendly manner if it's imperative that we stop what we are doing right away.
A: We're supposed to be studying, but we've been screwing around for the past hour.
B: I know. We'd better cut it out and buckle down. This exam is 60 percent of our final grade.
C: If I don't make at least an 80 percent on this exam, I'm screwed.
B: Alright. Should we start with our notes from Chapter 10?
C: That sounds like a good idea as soon as Alice tells us why she was kissing the professor.
A: I told you that wasn't me! Why don't you tell us why you were stalking the professor.
B: Ok guys. Cut it out. Let's get serious. We have one hour left to study.
sternly - strictly and seriously
imperative - important and necessary
screwing around - playing around, not being serious
buckle down - get serious and determined to do the work
screwed - in big trouble
as soon as - right after, soon after
stalking - following without being seen
Alright. Time to practice. Talk to you tomorrow.