1)To be attracted towards the same sex.
2)To be in a happy mood, joyfull, enjoying life.
3)A slang term for something bad.
I do not see why 'gay' is an insult, it is actually something the council (or something) produced to try to erase the discrimination towards homosexualists. 'Gay' actually means 'Good As You'.
1)"I'm sorry, I'm gay"
2)"She was in a gay ol' mood!"
3)"Geez, this place is so gay!"