I had a chance to hear that term quite a lot recently, but the meaning is not always the same.
For me, a senior developer is someone who has more responsibility compared to other developers he is working with (usually because he is the type of person who wants more responsibility and has the ability to handle it).
As it turns out, for employers it has a completely different meaning:
- In large organizations (such as banks) there are two types of developers: "regular" developers, allowed only to code, and senior developers, doing also designs. Working on design as a part of the job definition may look trivial to someone who never worked in such a company, but it's not the case in those organizations.
- Employers looking for someone experienced and wanting to avoid interviewing people with a chance of failing a "FizzBuzz" test. In contrast with my view of the term, the entire development team in such company may be composed of "senior developers".
If you take the second definition, I think that after you have been a developer for a while (let's say 5 years), every position you filled and every position you are looking for can be said to be "senior", depriving the term of all meaning.
What does "Senior Developer" mean to you?