Machine (n.) is a replacement for the confusing notion of 'subject'. Famously, the very connection between a child's mouth and a mother's breast, coming together, we might call a 'nourishing machine'.
The Machine (n.) is abstract because the asignifying signs with which it concerns itself lack determinate form or actual content definition. Though abstract, they are not unreal. They are in transport. They constitute the dynamic 'matter' of expression.
A Machine (n.) is an assemblage of parts that works and produces.
A Machine (n.) is any point at which energy enters or leaves a structure, connecting it with another structure.
A Machine (n.) is just any structure understood dynamically.
Machine (n.) is opposed not to organism, but to theater. The machine (e.g. Book, person, etc.) is a machine and not theater because it 'produces' desire rather than represents it upon a stage.