To throw up means to vomit: when your stomach forces food and liquid back up through your mouth. You might throw up when you're sick with the flu, ate something bad, or felt too much motion on a spinning carnival ride. Your body uses throwing up as a way to get rid of something it thinks is harmful or dangerous.

When you feel like you're about to throw up, you might feel nauseous, dizzy, or like your stomach is churning. It's an unpleasant experience, but it's actually your body protecting itself. After throwing up, many people feel better, almost relieved, because whatever was bothering their stomach is gone.

People use many informal expressions for throwing up: puking, being sick, upchucking, or saying someone lost their lunch. You might also hear adults say someone is feeling under the weather when they're nauseous but haven't thrown up.

The phrase can also mean tossing something upward, like when a basketball player throws up a shot at the buzzer, launching the ball high toward the basket in hopes it goes in.