This page, which describes the move known as a Jumping Jack, is part of the Turnstep Dictionary at www.turnstep.com.
A Jumping Jack is simply jumping up and spreading your feet, then jumping up and bringing your feet back together. The traditional arm movement is to start with arms at your side, raise them over your head on count 1, drop them to your side on count 2, raise over your head again on count 3, and drop them to your side again on count 4.
You may also see this move called a "star jump" or a "side-straddle hop". A variation is to spin in the air, so that you face the opposite direction at count 2, and have made a complete circle by count 4. This move can be done carefully on top of a bench, but never with the spin variation.
This move is done in 4 counts: