Cyber is a technology mediated domain of human and systems interactions.
Human <-> Human
Human <-> System
System <-> System
Human being biological entity as sender, receiver, sensor, perceiver.
System being a technology as sender, receiver, sensor, perceiver.
Why cyber? The overused and nearly useless word “cyber” exists to capture the technological risks and issues in systems of systems design. It is needed to define the varying interactions and exploits of systems. Cyber is not the electromagnetic spectrum, the network, or the computer. Cyber is facilitated and part of each but is more than signals on a wire. An attack using data with zero interaction with the adversary such as ballistic tables created for artillery is most assuredly a cyber existent capability. When thought of in traditional sense this is difficult to understand, but when you make the same assessment based on lasers, high value probabilistic targeting of trajectories taking out inbound missiles, the value of processing power becomes a unique capability.
This is not an exhaustive discussion, but an explanation to point to the fact that human to human interaction where an exploit takes the guise of social engineering to allow for exploit of a information asset is also cyber. Whether simply a human to human exploit would count is a point of solipsistic discussion. This construct also shows that two automated systems exploiting each other would be cyber in nature. There is zero requirement that this be a network, computer, or traditional information system. Hollerith cards are a data management system that store non-human readable information for computational system use.
The original idea of “cyber” was to place an umbrella over a set of unique capabilities so they could be discussed capturing that uniqueness. The ubiquitousness of information systems, and signals systems was a known challenge that this umbrella was meant to capture. Instead as can happen, they became the defining element subsuming many other aspects such as information operations (the military version of subversion and social engineering). If cyber is a domain then the definition needs to be wide enough to outlast the current generation of computing constructs and human activities.
Now about those “cyber dolphins” the navy uses.