This is not only unprofessional, but straight up offensive. If your demeanor is even close to similar in conversations with other peers or prospective employers, you will have a very difficult time being taken seriously.
Also I'm not even sure how this can be a real question.
Anybody who has the slightest understanding of startups knows the majority of them cease to exist within a few years of founding. There is no complex explanation needed beyond "the startup I was at closed its doors".
This is not only unprofessional, but straight up offensive. If your demeanor is even close to similar in conversations with other peers or prospective employers, you will have a very difficult time being taken seriously.