What's gossip?
Gossip is where you're talking about other people for no productive reason.
What's not gossip?
1. Analyzing a situation
2. Discussing how to help someone having a hard time
3. Trying to figure out what happened recently
4. Trying to decide if to bring someone closer in your life
5. Working through challenges you're having with an important person in your life
6. Genuinely positive updates about what people are doing
7. Looking at how a person managed to achieve something worthwhile
8. Otherwise important updates that are relevant to the listening party
There's perhaps a few other categories, but it's easy to go off the rails into discussing someone -- positively or negatively (but usually negatively) in a gossipy way.
The real problem with gossip isn't that it's morally terrible; it's that it's a big waste of time.
Conversations about other people who aren't there, that are started with no possible productive purpose... they usually wind up degenerating quickly to the lowest of common denominators, and wasting an entire possible conversation.
Empirically, engaging in gossip also seems more likely to make you into a more negative person.
There's millions of interesting things in the world, and millions of immediately important conversations to have about how to improve your life, and the life of your loved ones and the people you're responsible for.
Skip the conversations about the people you're not responsible for at all, when there's nothing to be learned or gained.
(Note: This is harder than it sounds, because other people like to gossip. You learn, over time, how to put the kibosh on it explicitly with people willing to be called out, and how to move past it gracefully with people who aren't. It does take practice and awareness to stop gossiping.)