seesaw

a plaything consisting of a board balanced on a fulcrum; the board is ridden up and down by children at either end

A play among children in which they are seated upon the opposite ends of a plank which is balanced in the middle, and move alternately up and down.

ride on a plank

move up and down as if on a seesaw

move unsteadily, with a rocking motion

To move with a reciprocating motion; to move backward and forward, or upward and downward.

To cause to move backward and forward in seesaw fashion.