Which qualities or skills define a Sr. Developer?

I'd say a lot of it centers around your ability to think through the whole problem, and develop a skillset for understanding what problems lie ahead based on how the task at hand is approached, and this comes with experience. Even the most talented non-senior developers don't seem to really have the ability to avoid coding themselves into a corner sometimes. Basically, someone needs to be able to see the forest, while it's okay if other team members focus on the trees.

On the other hand, it's really a title more than anything and for what it's worth I've always been more comfortable having a title conform to me rather than the other way around. Skills-wise though, I feel like you start crossing the chasm when you start feeling comfortable predicting what lies ahead and being comfortable enough with the material at hand that you can really apply your full creativity to problem solving.

There have been a few other articles and discussions on this topic, so I'd definitely recommend a few searches for some more insights, but always happy to take the topic fresh.