Considering descriptive (and not necessarily applied) physics, would it be proper to define resonance as:
"One of the fundamental means of storing energy" ?
Of course there are other ways to store energy like pressurizing a gas, charging a capacitor or creating chemical bonds for examples.
This wiki article on energy storage doesn't mention resonance anywhere as a means of storing energy, but only briefly when discussing applications it mentions resonance to
.. tune radios to particular frequencies.
In all the examples of resonance I'm able to imagine, resonance 'traps' energy in an object or system, so in a sense the structure of the object or system that enables resonance allows the storage of energy. As one simple example, a mass-spring system stores some initial energy introduced by compressing or extending the spring, and that energy, assuming no dissipative losses flows between potential and kinetic states indefinitely.
Of course there are usually dissipative losses in real resonant systems, but I can think of at least a few examples where the losses are small compared to the systems ability to trap the energy.
I don't believe there are any examples of resonance where energy is not being stored [within the bounds of the system].