GNU Collaborative International Dictionary of English

Found one definition

1.       
   Jumping jack.
   1. A toy figure of a man, jointed and made to jump or dance by means of strings or sticks attached to it.
   
   [1913 Webster]
   
   
   2. A calisthenic exercise in which a person starts in a standing position with both feet together and with the arms at the sides, then leaps into the air while moving the arms outward and upward so that the hands touch above the head, and then returns to the original position by reversing the motion of legs and hands.
   
   [PJC]