A phrase used almost exclusively by gay men(perhaps lesbians dont have this problem is much) to describe someone they feel would make a wonderful partner. Alas, said person is on the opposite end of the Kinsey scale, and just doesn't like men that way. Just to make things worse, a lot of tragically straight guys are very friendly and open-minded, and might even be flattered by your attention. It just meaningless to them.

Also a leading factor in gay teen suicide. When a teen feels that the person they love could never love them back because they're straight, it can cause some serious emotional harm.

Then again, it's not really a choice so it's not that person's fault. Also, there is tragically gay, usually experienced by women who have a craving for that... forbidden fruit.

We all go through it. It isn't the end of the world. Eventually, you just have to come to terms with it and understand that you can't always have your way, and just like for anyone else, some people just will never be interested in you.