2.5D

Short for “two-and-a-half-dimensional,” the term 2.5D Perspective is used for  projection techniques which simulate the appearance of 3D in a 2D environment. Examples include Axonometric Projection and Oblique Projection, which both rotate the viewpoint slightly to reveal multiple facets of objects in view.

Also: 3/4 Perspective, Pseudo 3D

[wikipedia: 2.5D]