The concept of a "dungeon" in video games has gotten kind of nebulous. Let's take Dungeon Defenders II, for instance. Sometimes they're actually in a dungeon, building traps and wasting goblins who are assaulting it. They are truly defending a dungeon. Sometimes they've set up shop in a mine, which, sure. It's a little abstracted, but it's got a "dungeon-y" feel to it. But sometimes those deformed adventurers are just building stuff out in a field and waiting for baddies to come marching on. That's not a dungeon, people!