somersault
An acrobatic roll where your body flips head over heels.
A somersault is an acrobatic move where you roll your body in a complete circle, going head over heels. When you do a forward somersault, you tuck your chin to your chest, roll forward onto your upper back, and continue the rotation until you're on your feet again. A backward somersault works the same way, just in reverse.
Gymnasts perform somersaults on mats and balance beams. Divers execute somersaults in mid-air before entering the water. Even young children naturally discover how to somersault when playing on grass or other soft surfaces. The move requires you to make your body compact, like curling into a ball, so you can rotate smoothly.
You'll also sometimes see it written as somerset, though that's less common today. People also use somersault as a verb: a skilled gymnast might somersault across the entire length of a mat.
Beyond the physical move, people say their stomach did a somersault when they felt nervous excitement, like the flipping sensation you get on a roller coaster or before performing in front of an audience.