Webster's Revised Unabridged Dictionary · 1913

Seesaw

Seesaw , noun

[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.
2.
A plank or board adjusted for this play.
3.
A vibratory or reciprocating motion.
He has been arguing in a circle; there is thus a seesaw between the hypothesis and fact. — Sir W. Hamilton
4.
(Whist.) Same as Crossruff.

Seesaw , intransitive verb

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

Seesaw , transitive verb

To cause to move backward and forward in seesaw fashion.
He seesaws himself to and fro. — Ld. Lytton

Seesaw , adjective

Moving up and down, or to and fro; having a reciprocating motion.