Thinking about it further, since it means "independent," I would consider any game where the devs had an idea for a game and made that game without corporate meddling compromising their vision to be considered "indie," and if that includes some games by big studios like Valve or Nintendo, then so be it. It's a huge deal to be able to make a game like that nowadays, regardless of how much funding they had. There can be "small indie" and "large indie" games.