A run with no additional completion requirements; anything goes. The "default" category for speedrunning a game. The term comes from the old school Metroid speedrunning community. Metroid has a percentage counter, while other games may not, but the term stuck around.
Most games are any% these days. 100% would be if you finish every quest and don't just skip the optional ones (like Bloodraven). It's not popular in most games, and especially not in D2.