Perturbation
Perturbation , noun
[Latin perturbatio: compare French perturbation.]
1.
The act of perturbing, or the state of being perturbed; esp., agitation of mind.
2.
(Astronomy) A disturbance in the regular elliptic or other motion of a heavenly body, produced by some force additional to that which causes its regular motion; as, the perturbations of the planets are caused by their attraction on each other. — Newcomb