Powerbuilding simply means intelligently combing some aspects of powerlifting and bodybuilding together. Generally, this will mean:
1. Using the big 3 lifts as the foundation of the program – squat, bench, deadlift
2. Max effort work – Incorporating specific heavy lower rep range targets more common to powerlifting
3. Dynamic effort work – Incorporating some medium weight dynamic speed work that powerlifters use for rate of force development
4. Using isolation work that is more common for bodybuilders
5. Using more of a variety of movements in order to achieve maximal development of each muscle group common for both powerlifters and bodybuilders
6. Incorporating medium to high rep pump work more specific to bodybuilding
Combine all this intelligently, and you get powerbuilding.