What is the definition of human layer?

The OSI (Open Systems Interconnect) 7-layer model describes all of computing and communication. The layers range from the physical wire, at the lowest layer, layer 1, up through applications (apps) at the highest layer, layer 7. Each higher layer uses each lower layer for computing and communication purposes.

But who uses applications? Humans. So the human layer is the unspoken 8th, highest, layer of the model.