Most know that the idiom "jumping the shark" is a bad thing. Some know what it means; many think they know what it means; and many more have no clue what you are talking about when you say it. So, what does it really mean? Specifically, it references a HAPPY DAYS episode where Fonzie water ski-jumped over a shark.
Jumping the shark is the moment where you realized that the show had lost the foundation of its creativity that had kept it a quality show up to that point. It is when the writers diverted from the established logic of the show and entered into the realm of absurd-show-logic Consider it the sign that things were going down hill. The writers were fresh out of good ideas and were now just milking the episodes for as long as possible so they could keep the money coming in. People can argue when or where a show jumped the shark, but these arguments should be saved for AFTER the show has either gone off the air, or it has been in a downward slide for many seasons. Declaring that something has "jumped the shark" after one episode is ridiculous, even though people enjoy doing it.
For CHUCK fans, there is a different idiom that is pronounced very similarly: "Jumping the Shaw-arc" is when the show righted its path and rediscovered what made people love it. I know quite a few hardcore fans who were questioning their love for the show during the Shaw/Sarah romance arc, who felt rejuvenated once it ended. Though, there are still those who abandoned the show during that time who might want to revisit it in season 4. I think it is safe to say that the final six episodes of the season, post jumping of the Shaw-arc, were the type of quality, fun, drama, and storytelling we expect from this show.
So, gather up your friends and enemies and tell them the good news: CHUCK jumped the Shaw-arc. Everything is fine now. It is safe to swim in the water again. No large piece of wood will harm you ever again, nor splinter poor Sarah "Sam" Walker.
*Let me add that I loved Shaw as a bad guy and would welcome his return as one.