my mistake about the incident being shown on the PPV...
anyway, a zipline is a cable where a carriage is put on for someone to grab onto and come down on.. sort of like the "flying fox" thing in NS...
here's the 1Wrestling.com Q&A on the incident:
Q: Having only been a WWF fan for about a year, I'd like to know more about the tragic passing of Owen Hart. What show did this happen at? Who was his scheduled opponent? In terms of the storyline, why was he rappelling from the ceiling anyways? And, should he have survived, what do you think would be of him today?
A: It happened at the WWF's "Over The Edge" Pay-per-view on Mat 23, 1999 in Kansas City, MO at the Kemper Arena. Owen was scheduled to wrestle The Godfather in his "Blue Blazer" persona. The Blue Blazer, a superhero gimmick that Owen had used in his initial WWF run, was brought back as a comedy gimmick, not that much unlike the Hurricane gimmick of today. At the PPV, Owen was to make a "superhero-like" entrance by being lowered into the ring on a cable. His tragic fall was not seen on the PPV broadcast, since a pre-taped interview was being shown at the time. Sadly, we'll never know what Owen would have done in his career had it continued. He might have remained a solid hand in the WWF, or he may have eventually jumped to WCW, or perhaps he would have just retired. We'll never know.