somersault in British English
or summersault (ˈsʌməˌsɔːlt)
noun1. a. a forward roll in which the head is placed on the ground and the trunk and legs are turned over it
b. a similar roll in a backward direction
2. an acrobatic feat in which either of these rolls are performed in midair, as in diving or gymnastics
3. a complete reversal of opinion, policy, etc
verb4. (intransitive) to perform a somersault