Толковый словарь английского языка - seesaw

I. noun Etymology: probably from reduplication of 3saw Date: 1704 an alternating up-and-down or backward-and-forward motion or movement, 2. a pastime in which two children or groups of children ride on opposite ends of a plank balanced in the middle so that one end goes up as the other goes down, the plank or apparatus so used, ~ adjective II. verb Date: 1712 intransitive verb 1. to move backward and forward or up and down, to play at ~, alternate , transitive verb to cause to move in ~ fashion