So guys
 

I don't get it. What's Alternative.

Coldplay.

Not any more.

i would say alternative is the opposite of mainstream. although now alternative is becoming a more and more popular term it's starting to not make sense.

Fixed.

alternative is what it says: alternative, which is to say, another option to listen to instead of the mainstream.

of course, the term has now been abused so that mainstream music is labelled "alternative". that's just marketing bullsh1t. what the term is really supposed to refer to is that which follows from its linguistic meaning.

Well, I mean, you get bands like Dinosaur Jr. and REM put together in Alternative, and then maybe TV On the Radio, who don't really have similar sounds. Is it just a catch all term that means something different?

PS: Loving those first two answers.

It's a catch-all term that mean basically nothing.

A pointless term that's about 20 years past it's sell by date that never really meant anything in the first place.

merriam-webster:

3: different from the usual or conventional: as a: existing or functioning outside the established cultural, social, or economic system <an alternative newspaper> <alternative lifestyles> b: of, relating to, or being rock music that is regarded as an alternative to conventional rock and is typically influenced by punk rock, hard rock, hip-hop, or folk music c: of or relating to alternative medicine <alternative therapies>