There are two definitions
1) a person who likes to dress and act differently to the other people in society, normally in black but some like much brighter colours. They tend to be thinkers and more often than not quite creative. They have a satyrical sense of humour, and are able to laugh at both themselves and other people. This type of goth originated in the late 80's with the "death" of punk; goths back then liked the style and the "protection" it offered and so emulated it in their own style. They listen to and appreciate all sorts of good music. They can be gay/depressed/weird/mentally disturbed, but more often than not they are just normal people.
2) an offshoot of the nu-metal clique who think that to *really* piss off their parents they'll dress all in black and talk about death and suicide whilst listening to Limp Bizkit, Linkin Park and Slipknot because it's "cool". They tend to have very little idea of the other type of goths (or anything else other than themselves for that matter) and will probably change their fashion once it becomes "uncool" again. Thank god.
1) I like this kind of goth and aspire to it.
2) I am not a "goth".