Yea words have meanings. And since you know what you're talking about the "Big Crunch" shouldn't be anything new to you right? So there's no need in telling you what it exactly is right? Because you know what you're talking about. Let's just skip to the last part of the "Big Crunch" when every matter of the universe is a sigularity. It is possible that this sigularity would make a new Big Bang (this is probably what created the universe but I think you know better) which would mean the universe is reborn. But we (humans) don't know if it's possible or if the "Big Crunch" is even a thing. So there is this little funny word we use. Uhm what was it again? Ah yes. THEORY. I forgot that words have meanings. So sorry.