If someone is unavailable, they are not able to talk to people or meet people, usually because they are doing other things.

News outlets tried to contact the Senator, but she was unavailable for comment. 新闻机构试图联系参议员，但是她无暇发表评论。

If something is unavailable, you cannot get it or use it.

This information was previously unavailable to the public. 这样的信息以前公众是无法获知的。