Vault Over Someone’s Back

Word Meaning:

LEAPFROG — (games) A game, often played by children, in which a player leaps like a frog over the back of another person who has stooped over. One variation of the game involves a number of people lining up in a row and bending over. The last person in the line then vaults forward over each of the others until they reach the front of the line, whereupon they also bend over. The process is then repeated.

Definitions from Wiktionary.