If the device was built to accelerate the electron in the cyclotron, the frequency has to be matched with the frequency for the electron to move around in the device. It is the frequency of the power supply should match the cyclotron frequency if the magnetic field is fixed (and normally this is the case). So I would define "cyclotron frequency" as qB/(2*pi*m) which is a property for the device, instead of the frequency for the electric field applied between the dees, which could be changed from the power generator.