I guess that you will have to search the various engine manuals to see if they use the term overboost
In engineering venacular it is used to apply to a condition where any of the critical parameters are exceeded in the gas generator. the idea of the engine control system is to protect against these exceedances to an extent.
In the rotors it's an overspeed that is the concern. Too much RPM can get you into big trouble with the vibratory integrity of critical rotors (Ala the National airlines, DC10/CF6 that spewed out the fan blades)
Too much overtemp and you could burn out the turbine (pretty common)
Too much overpressure is unlikely to be a problem on its own (the engine cases have margin) but it typically comes with baggage like overtemperature as well