What does shake off their sterile curse mean in Julius Caesar?

The phrase "shake off" in the context of Julius Caesar means to get rid of or discard something completely. In this case, it refers to discarding the "sterile curse" which Brutus and Cassius are planning to place upon Octavius Caesar. The curse is a metaphor for the consequences or punishment that Brutus and Cassius believe Octavius will face if he opposes their plans. They are determined to ensure that Octavius is punished for any attempts to thwart their conspiracy against Caesar. By shaking off this sterile curse, Brutus and Cassius are expressing their intention to confront and defeat Octavius, regardless of the consequences.