*seesaw*

n. [ Probably a reduplication of saw, to express the alternate motion to and fro, as in the act of sawing. ] 1. 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. [ 1913 Webster ]

2. A plank or board adjusted for this play. [ 1913 Webster ]

3. A vibratory or reciprocating motion. [ 1913 Webster ]

He has been arguing in a circle; there is thus a seesaw between the hypothesis and fact. Sir W. Hamilton. [ 1913 Webster ]

4. (Whist.) Same as Crossruff. [ 1913 Webster ]