The Collaborative International Dictionary of English v.0.48:

Teeter \Tee"ter\, v. i. & t. [imp. & p. p. Teetered; p. pr. &
   vb. n. Teetering.] [Prov. E. titter to tremble, to seesaw;
   cf. Icel. titra to tremble, OHG. zittar[=o]n, G. zittern.]
   To move up and down on the ends of a balanced plank, or the
   like, as children do for sport; to seesaw; to titter; to
   titter-totter. [U. S.]
   [1913 Webster]

         [The bobolink] alit upon the flower, and teetered up
         and down.                                --H. W.
                                                  Beecher.
   [1913 Webster]

WordNet (r) 3.0 (2006):

teeter
    n 1: a plaything consisting of a board balanced on a fulcrum;
         the board is ridden up and down by children at either end
         [syn: seesaw, teeter, teeter-totter, teetertotter,
         teeterboard, tilting board, dandle board]
    v 1: move unsteadily, with a rocking motion [syn: teeter,
         seesaw, totter]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "teeter":
   Lissajous figure, alternate, alternation, back and fill,
   back-and-forth, balance, battledore and shuttlecock, change,
   come and go, coming and going, cower, dither, dodder, ebb and flow,
   equivocate, falter, flounder, fluctuate, flux and reflux,
   go through phases, halt, hitch and hike, limp, lurch, metronome,
   oscillate, oscillator, pass and repass, pendulate, pendulum,
   quiver, reciprocate, reciprocation, rhythmic play, ride and tie,
   ring the changes, rock, rocker, rocking chair, rocking stone,
   seesaw, seesawing, shake, shift, shilly-shally, shuffle, shuttle,
   shuttlecock, sine wave, stagger, stammer, stumble, sway, swing,
   teeter-totter, teeter-tottering, teeterboard, teetering,
   teetery-bender, tergiversate, to-and-fro, topple, totter,
   tottering, tremble, turn, ups and downs, vacillate, vary, vibrator,
   waver, wax and wane, weave, wibble-wabble, wigwag, wobble,
   zigzag