I use the term “chief executive” as a synonym for “President”, “Chancellor”, “First Secretary”, etc.
This revolt may or may not include a substantial portion of the aristocracy and it may or may not be encouraged by foreign governments.
The rebellion is distinguished from the coup d'etat by being generally unplanned and involving a sizable percentage of the general population, in other words, people outside the present government.
The Islamic and Russian Revolutions both started with a broader base of support and then were taken over by one of the revolutionary groups which came to control the government. The Islamic Revolution started as a rebellion against the Shah's government but was only later taken over by orthodox Shia. The Russian Revolution first resulted in the Kerensky Provisional Government and was later taken over by the Bolsheviks.
The coup d'etat has in the past been a device of intelligence agencies of various nations attempting to execute regime change on a country that is not their own.
Sometimes we are not sure whether a chief executive was assassinated. An example of this is the death of Joseph Stalin who may or may not have been poisoned by Beria.