The Collaborative International Dictionary of English v.0.48:

cartwheel \cartwheel\ n.
   1. the type of wheel used on a cart; it typically has wooden
      spokes and a metal rim.
      [WordNet 1.5]

   2. an acrobatic maneuver in which the arms and legs are
      outstretched like the spokes of a wheel, and the body is
      turned sideways through one or more revolutions, by first
      touching the hands and then the feet to the ground, in
      rapid succession so as to mimic the rolling of a wheel; in
      the course of this feat, the person performing it is
      alternately upright and upside-down.
      [WordNet 1.5 +PJC]

   3. a silver dollar; a dollar made of silver. [Colloq.]
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

cartwheel \cartwheel\ v. i. 1
   to perform a cartwheel[2].

   Syn: do cartwheels.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

cartwheel
    n 1: a wheel that has wooden spokes and a metal rim
    2: acrobatic revolutions with the body turned sideways and the
       arms and legs outstretched like the spokes of a wheel
    3: a dollar made of silver [syn: silver dollar, cartwheel]
    v 1: do cartwheels: perform an acrobatic movement using both
         hands and feet