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]