Yes, I would say the most common definition is: "Homosexual". Most english-speaking adults know that another definition is "happy", but I personally have never heard anybody use it that way in a sentence. Only in literature. In America some people, especially young people, very informally, use "gay" to mean "poor quality, stupid or ridiculous". Examples: That movie we saw was so gay!" Meaning it was stupid or poor quality. But this is not really an acceptable way to use it. It think that is what Erica means.

That is technically correct, but gay is not really used anymore to describe emotion. You might come across it in old poetry or song lyrics, but it is mostly used to describe one's sexuality. Just be careful because using gay to describe something negative (such as saying "that's so gay") is very offensive to many people.

Teenagers today use the word 'gay' to mean that something is bad. Example: Oh that singer's music is so gay. In comparison they say something is 'fully sick' to describe something wonderful. Example: That band was fully sick last night.

Correction: "gay" WAS "happy"! Even if you say, "I was so gay(=happy) in my younger days", people will still get the double meaning of happy and homosexual. Plenty of jokes have been written around this double meaning. Generally, "gay" now means "homosexual". If any word has very different meanings, or is confusing, I advise finding a different word. Don't always believe what the dictionary tells you! ;)

maybe~