also known as: Axonometric projection.1)
Isometric/Asonometric projection is a way of representing three-dimensional space without realistic perspective, where more than face of an object becomes visible.
More commonly games described as such will use oblique projection, but 'isometric' is an effective term for discussing games with a skewed, three-dimensional perspective. Most typically characters in these games will be restricted to diagonal movements, and the awkwardness of these being an important mechanic in some action/adventure games.
For games using their own perspectives, of where parts are rendered in conflicting types.