An impulse is a sudden, strong urge to do something without thinking it through first. When you feel an impulse to blurt out an answer in class before raising your hand, or grab a cookie when you're supposed to wait until after dinner, that's your impulse talking. It's that quick feeling that says “do it right now!” before your brain has time to consider whether it's actually a good idea.

Everyone experiences impulses. You might feel an impulse to pet a cute dog you see on the street, or an impulse to spend your birthday money the moment you get it. Some impulses are worth following and some aren't. Following your impulse to help a friend who dropped their books makes sense. Following your impulse to push to the front of the lunch line doesn't.

The word can also mean a sudden force or push. In science, an impulse describes a quick application of force, like the impulse that sends a soccer ball flying when your foot strikes it. Your heart sends signals through your body with electrical impulses. These physical impulses happen fast and create immediate effects, just like the mental kind.