perturbation

(noun) an unhappy and worried mental state. Synonyms: disturbance, upset. Examples: "There was too much anger and disturbance." "She didn't realize the upset she caused me."

(noun) (physics) a secondary influence on a system that causes it to deviate slightly.

(noun) activity that is a malfunction, intrusion, or interruption. Synonyms: disturbance. Examples: "The term `distress' connotes some degree of perturbation and emotional upset." "He looked around for the source of the disturbance." "There was a disturbance of neural function."

(noun) a disposition that is confused or nervous and upset. Synonyms: fluster.

(noun) the act of causing disorder. Synonyms: disruption.