You could talk about indie-labels and independent music. However, Hip-Hop, dance music, a lot of metal, most jazz after the 60's-70's not to mention blues, folk (NOT indie-folk), "world music¤", a lot of country outside of the nashville-trends etc. never really got the "indie" tag despite primarily being put out on independent labels.

I'd say it has its roots in the DIY aspects of the punk-scene and the music that followed in its wake which was stuff like post-punk, No Wave, New Wave, post-hardcore, noise rock, 80's jangle or psych revival, college-rock/"alternative" etc. The distinction between indie and alternative came when bands with stereotypical "indie"-sounds in the context of the 80's (think REM, Replacements, Husker Du, Pixies etc.) started toget signed to major labels. Then they were obviously not "indie" anymore but their music still sounded different from the mainstream music-trends of the time (=80's). Hence:alternative.

Anyway, ''indie'' as a genre-tag has pretty much always meant this type of stuff. The problem, just as with alternative in the 90's, is that the name became inappropriate. I mean, what are you an alternative to when your music is the sound of mainstream rock? And how can you be indie on a major label? It's static genre-definitions with dynamic names...