What is Axonometric Projection?

Legal Definition
Axonometric projection is a type of parallel projection used for creating a pictorial drawing of an object, where the object is rotated along one or more of its axes relative to the plane of projection.

There are three main types of axonometric projection: isometric, dimetric, and trimetric projection.

"Axonometric" means "to measure along axes". Axonometric projection shows an image of an object as viewed from a skew direction in order to reveal more than one side in the same picture. Whereas the term orthographic is sometimes reserved specifically for depictions of objects where the axis or plane of the object is parallel with the projection plane, in axonometric projection the plane or axis of the object is always drawn not parallel to the projection plane.

With axonometric projections the scale of distant features is the same as for near features, so such pictures will look distorted, as it is not how our eyes or photography work. This distortion is especially evident if the object to view is mostly composed of rectangular features. Despite this limitation, axonometric projection can be useful for purposes of illustration.

In German literature, oblique projection is also considered an axonometric view, per Pohlke's theorem of axonometry.

In some English literature, axonometric projection is considered a sub-class of orthographic projection.
-- Wikipedia
Legal Definition
1. a projection that shows an ojects three dimensions. The axes are oriented relative to the projected surface. 2. A 3d drawing of a building based on a floor plan. The lines are parallel so perspective is not considered.