Leapfrog is a game in which players vault over each other's stooped backs.
The number of participants is not fixed.
The first participant rests hands on knees and bends over, which is called giving a back. (Games of this sort have been called by this name since at least the late sixteenth
century.) The next player places hands on the first's back and leaps over by straddling legs wide apart on each side. On landing he stoops down and a third leaps over the first and second, and
the fourth over all others successively. When all the players are stooping, the last in the line begins leaping over all the others in turn.