revolt against God: a turning away from him, and the talk that pushes others into it
This is a noun built from the verb meaning to turn aside, leave, or be taken away (סוּר). It does not picture an uprising or a coup. It pictures people walking off the road they were given, away from the God they belong to, and it became the prophets' standard name for that walking away.
Almost every time the word appears, someone is talking. Deuteronomy makes a prophet who has "spoken" it liable to death. Jeremiah uses the same wording twice in sentences passed on prophets who told Judah what it wanted to hear. Isaiah lists it among the things a guilty people say out loud. So the word names both the desertion and the persuasion that produces it, which is why English versions have to shift between "rebellion", "revolt", and "turning away" from verse to verse.
Isaiah shows how far the idea stretches. In one place a beaten people simply keep adding to it, so that more punishment would change nothing. In another they have gone deep into it, so that coming back means climbing out of a hole they dug. The word describes a direction of travel more than a single act, which is why it can be piled up, deepened, and preached.