WordNet (r) 3.0 (2006):

rocking horse
    n 1: a child's plaything consisting of an imitation horse
         mounted on rockers; the child straddles it and pretends to
         ride [syn: hobby, hobbyhorse, rocking horse]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "rocking horse":
   agate, ball, baseball bat, bat, battledore, bauble, blocks,
   checkerboard, chessboard, club, cockhorse, cricket bat, cue, doll,
   doll carriage, gewgaw, gimcrack, golf club, hobbyhorse,
   jack-in-the-box, jacks, jackstones, jackstraws, kickshaw,
   knickknack, marble, marionette, mig, paper doll, pick-up sticks,
   pinwheel, plaything, puppet, racket, rag doll, sport, steelie, taw,
   teetotum, top, toy, toy soldier, trinket, whim-wham