What do you mean? What have you got to be disappointed about?

你什么意思 你有什么可遗憾的？

If you use this adjective it means, you are disappointed about something, but you do perhaps understand the reason for it.

如果你是用这个形容词，那么你对某事很失望，但是你也许确实了解其中的缘由。

Although Albert was disappointed about that, he should not have been surprised.

尽管阿尔伯特对此感到失望， 但他不应该感到惊讶。