Thanks, @Justin.

Indeed, the "senior" title lost its true meaning but we can also justify it with the fact that there is no clear/agreed-upon definition.

Giving an age for a senior engineer isn't a great approach. Some developers started their careers late. They might be in their forties but they only started with coding as a career only a few years ago. Does that make them seniors? Not to mention that some individuals lie in their CV about their previous experience.

On the other hand, some other developers started quite early. For instance, I built and sold my very first software to a small business when I was 16 years of age. I'm under the age you "defined" though.

I think to be a senior you need knowledge (usually in the technologies required by the job), skills and attitude.