BloodyDemise Posted:

a tv show ‘jumps the shark’ when some ****ty gimmick or plot twist is introduced, generally to save the writers’ bumes, forever ruining the show

That’s the most common way, but in general it means any time a TV show has started to go downhill forever, and has come to mean anytime anything has pbumed it’s peak.

From Jumptheshark.com (circa 1999)

It’s a moment. A defining moment when you know that your favorite television program has reached its peak. That instant that you know from now on…it’s all downhill. Some call it the climax. We call it jumping the shark. From that moment on, the program will simply never be the same.

They created the term when Fonzie jumped over a shark on water skis in Happy Days.