jumping jack

Short definition from Wiktionary

Noun

1. 1
   A physical exercise performed by jumping to a position with the legs spread wide and the hands touching overhead and then returning to a position with the feet together and the arms at the sides.
2. 2
   A machine, roughly the size of a three-year-old child, the foot of which vibrates forcefully, causing it to "jump" rapidly, pounding the ground to compact it.
3. 3
   A toy figure of a person with jointed limbs that can be made to appear to dance or jump by pulling an attached string.
4. 4
   Alternative form of jumping jack.