To me, part of breaking a story is being ahead of the story -- informing readers what is going to happen, or what the team is trying to make happen. That's the game these days for many of us, especially with the instant scramble of Twitter. If you tell people what is going to happen an hour, a day, a week, two weeks ahead of time, reporting in real time as it begins and preparing readers for what is about to happen, that is as much a part of breaking a story and reporting a story as it is tweeting out a sentence.
Please keep in mind that different outlets have different priorities, and reporters have to respond to what their employers/editors want -- is it a tweet for Twitter or is it a complete article for your employer?
To me, staying ahead of the story is more an more important. Telling readers that the Cardinals are actively working on negotiating an extension, reporting the pitcher they're trying to sign, repeating how they're trying to pursue a trade. That's all part of breaking a story ahead of a done deal.
Breaking a story can also be being the first to report a significant scoop such as The Athletic's on the Houston sign-stealing or the New York Times' breaking the story on the hacking scandal. And they were broken with complete, well-researched, well-sourced stories.