Also known as "squat-thrusts" from your high-school PT days. The "official" burpee for CrossFit is explained in the standards video from the '08 Games. Here's a description of the burpee:

To perform a burpee with a pushup, you will begin in a squat position with hands on the floor in front of you

(1). Kick your feet back, while simultaneously lowering yourself into the bottom portion of a pushup. Your arms will not be extended.

(2). Immediately return your feet to the squat position, while simultaneously pushing "up" with your arms. You will perform a pushup as you return your feet to the squat position

(3). Leap up as high as possible from the squat position

(4). Repeat, moving as fast as possible.