The Collaborative International Dictionary of English v.0.48:

Merry-go-round \Mer"ry-go`-round"\, n.
   Any revolving contrivance for affording amusement; esp., a
   group of seats in the shape of hobbyhorses or other fanciful
   animals, arranged in a circle on a platform that is rotated
   by a mechanical drive, often to the accompaniment of music;
   the seats often move up and down in synchrony with the
   rotation; -- called also carousel. It is employed primarily
   for the amusement of children, and is typically found at an
   amusement park.
   [1913 Webster]

WordNet (r) 3.0 (2006):

merry-go-round
    n 1: a never-ending cycle of activities and events (especially
         when they seem to have little purpose); "if we lose the
         election the whole legislative merry-go-round will have to
         start over"
    2: a large, rotating machine with seats for children to ride or
       amusement [syn: carousel, carrousel, merry-go-round,
       roundabout, whirligig]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "merry-go-round":
   Ferris wheel, carousel, chute-the-chutes, chutes, disk,
   flying horses, mad round, roller, roller coaster, rolling stone,
   rotator, rotor, round of pleasure, roundabout, rundle, seesaw,
   swing, teeter-totter, the dizzy rounds, the rounds, top, wheel,
   whip, whirl, whirlabout, whirler, whirligig