Aviation overspeed

Pilots need to react without hesitation to an overspeed warning - usually by reducing the throttles to flight idle and therefore bringing the speed outside of the warning envelope

As Dean F mentioned in his comment, the FAA prohibits flight over 250kt below 10,000 ft MSL as a measure for traffic control

Coming to jet driven aircraft, overspeed conditions are attained when the maximum operating speed has been exceeded by the axial compressor of the engine

As a result, we notice mechanical failures of the turbine blades or flameouts or even complete destruction of the engine

Overspeed is that situation or condition of an aircraft in which it's engine is made or forced to operate beyond it's designed limits

However, the consequences that arise when a particular engine is made to run too fast vary depending upon the engine type and the model used