seesaw

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A long plank balanced on a central fulcrum so that with a person riding on each end, one end goes up as the other goes down. Also called regionally dandle, dandle board, teedle board, teeter, teeterboard, teeter-totter, tilt¹, tilting board. See Regional Note at teeter-totter.
2. n. The act or game of riding a seesaw.
3. n. A back-and-forth or up-and-down movement, as of the lead between two contesting parties.
4. v. To play on a seesaw.
5. v. To move back and forth or up and down.

Century Dictionary and Cyclopedia

1. n. A sport in which two children sit one at each end of a board or long piece of timber balanced on some support, and move alternately up and down. This amusement is of remote antiquity; it is familiar in Greek vase-paintings as a pastime, especially of girls older than the children who usually resort to it now.
2. n. A board adjusted for this sport.
3. n. Any process resembling directly or indirectly the reciprocating motion of the see-saw.
4. n. Especially.
5. n. A circular definition or proof; the definition of a word or thing by means of another which is itself defined by means of the first; the proof of a proposition by means of a premise which is itself proved from the first proposition as a premise.
6. n. In whist, the playing of two partners so that each alternately trumps a low non-trump card led by the other; a double ruff; a cross-ruff.
7. Reciprocating; reciprocal; back and forth, or up and down: as, a see-saw motion.
8. To move as in the see-saw; move backward and forward, or upward and downward; teeter: literally or figuratively.
9. To cause to move or act in a see-saw manner.
10. n. A motion of a steam-engine governor which oscillates on both sides of its mean or neutral position and causes the speed of rotation of the engine to vary above and below the mean.

Wiktionary

1. n. A structure composed of a plank, balanced in the middle, used as a game in which one person goes up as the other goes down; a teeter-totter
2. n. a series of up-and-down movements.
3. n. a series of alternating movements or feelings
4. v. To use a seesaw.
5. v. To fluctuate
6. adj. fluctuating.

GNU Webster's 1913

1. n. 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. n. A plank or board adjusted for this play.
3. n. A vibratory or reciprocating motion.
4. n. (Whist.) Same as Crossruff.
5. v. To move with a reciprocating motion; to move backward and forward, or upward and downward.
6. v. To cause to move backward and forward in seesaw fashion.
7. adj. Moving up and down, or to and fro; having a reciprocating motion.

WordNet 3.0

1. v. move up and down as if on a seesaw
2. v. move unsteadily, with a rocking motion
3. n. a plaything consisting of a board balanced on a fulcrum; the board is ridden up and down by children at either end
4. v. ride on a plank