Alternative to what?

I was in the car this afternoon doing something I rarely do: listen to the radio. That isn't to say I don't listen to music in my car; I just don't choose the radio as a source of music.

I noticed something very strange on one station I listened to today...their tagline is "Everything Alternative". I thought that I was listening to a late '80s cut. What the heck is "alternative" anymore?

Alternative certainly meant something in the '80s, when there was little variety in pop music. But what does this term mean today, when almost everything is an alternative to bland formulaic pop?

Of course today we have the opposite problem. No one knows how to define music genres. I took a look at AllMusic.com and found the following categories within the Alternative/Indie Rock genre:
Alternative/Indie-Rock

* Industrial
* Alternative Pop/Rock
* Goth Rock
* Lo-Fi
* Grunge
* Shoegaze
* Britpop
* Post-Rock/Experimental
* Funk Metal
* Indie Rock
* Paisley Underground
* Jangle Pop
* Punk Revival
* Post-Grunge
* Third Wave Ska Revival
* Neo-Psychedelia
* Riot Grrrl
* Space Rock
* Adult Alternative Pop/Rock
* Alternative Dance
* Cocktail
* Dream Pop
* Punk-Pop
* British Trad Rock
* Industrial Dance
* Madchester
* Psychobilly
* Ska-Punk
* Cowpunk
* New Zealand Rock
* Chamber Pop
* Twee Pop
* Emo
* Slowcore
* Ambient Pop
* C-86
* Indie Pop
* Noise Pop
* Math Rock
* Queercore
* Sadcore
* Shibuya-Kei
* Skatepunk
* Garage Punk
* Alternative Folk
* Neo-Glam
* College Rock
* Pop Underground
* American Underground

I'm pretty obsessed with music but I'm not sure that I know what about 1/3 of those are.