perturbation

noun

• 1anxiety; mental uneasiness:she sensed her friend’s perturbation
• a cause of anxiety or uneasiness:Frank’s atheism was more than a perturbation to Michael

• 2a deviation of a system, moving object, or process from its regular or normal state of path, caused by an outside influence:some minor perturbation in his house’s cash flow
• Astronomy a minor deviation in the course of a celestial body, caused by the gravitational attraction of a neighboring body.