I'm so shy to talk about this, but since you're asking, "horny" means "sexually aroused".. Whenever someone asks you "Are you horny?" it's like she's asking you if you want to make love (or have sex).. haha, hope this helps a bit :D

Some guys just don't know when it is their lucky day. Horny = 色迷

Why would she ask you this sort of question?

ｈｏｒｎｙ的意思是＂好色“

It is a physical state of body and mind, when you want to have sex. It is a slang. Hope it is clear. Regards.