LogFAQs > #923097145

Strictly speaking, a game is indie if it's not backed by a major publisher. There's some grey area there, like a number of games that were developed independently but picked up by a major publisher for distribution purposes, but that's the main criterion. In practice, it tends to just refer to any game that's lower-budget, hence games like Hellblade aren't typically considered indie despite the game having been published independently by Ninja Theory.