perturbation

perturbation is a   Noun

Definition:

[1] The act of perturbing, or the state of being perturbed; esp., agitation of mind.

[2] 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.

Synonyms: