Cartwheel:
a gymnastics skill in which the body makes a revolution sideways supported on the hands with arms and legs outstretched. A cartwheel is a basic skills in gymnastics and can be a progression (lead up) to round-offs and aerial cartwheels (a cartwheel with no hands).
View this video (courtesy of EHowSports) on how to do a cartwheel http://youtu.be/97RVWQ7FBt4