per|tur|ba|tion «PUR tuhr BAY shuhn», noun.
1. the act or fact of perturbing.
2. a perturbed condition: »
Though the violence of her perturbations gradually subsided, her cheerfulness did not return (Lytton Strachey).
3. a thing, act, or event that causes disturbance or agitation: »
The crown…O polish'd perturbation! golden care! (Shakespeare).
4. Astronomy. a disturbance in the motion of a planet or other heavenly body in orbit caused by the attraction of a body or bodies other than its primary: »
Perturbations, or disturbances in the motions, of the planets Neptune and Uranus first led…astronomers to hunt for a distant planet beyond Neptune (Science News Letter).
Useful english dictionary. 2012.