When is a startup no longer a startup?

I know this sounds like one of those useless philosophical questions - bear with me.

I returned yesterday from a job interview. My wife, who is naturally skeptical, asked how it went. "Well, they're a Series A startup. Maybe 50 people. The problem they're solving is really interesting..."

She immediately gave me the stinkeye upon the mention of the funding, then said "OK, fine. Whatever. So when does a startup quit being a startup? Is it when they get (insert eyeroll here) Series Z funding? What's the definition?"

I'm not really expecting an answer. I'm more interested in the points at which HN readers realized that their shiny new company was no longer shiny.

Honest question. Thanks for your thoughts.