The idiom "that ship has sailed" means that an opportunity has passed and it is too late to take advantage of it. It is often used to express regret or disappointment about a missed chance.
For example, if someone says "I wish I had invested in Bitcoin when it was still cheap," you could respond by saying "Sorry, but that ship has sailed. Bitcoin is now worth a lot more than it used to be."
The phrase comes from the idea of a ship leaving port. Once a ship has left, it is impossible to catch up to it or board it. Similarly, once an opportunity has passed, it is impossible to go back and take advantage of it.
Overall, "that ship has sailed" is a useful idiom for expressing that something is no longer possible and that it is time to move on.
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