perturbation

noun

natural processes relating to changes in the nature of water-borne alluvial sediments and in situ soil deposits over time
disturb, upset

Etymology: Borrowed from Middle French perturbation, from Old French perturbacion, from Latin perturbatio.

Agitation; the state of being perturbed.
“Reſtore your ſelues, vnto your temper, Fathers; / And, vvithout perturbation, heare me ſpeake: […]”
“But her mind had never been in such perturbation; and it needed a very strong effort to appear attentive and cheerful till the usual hour of separating allowed her the relief of quiet reflection.”
A small change in a physical system, or more broadly any definable system (such as a biological or economic system).
“Natures that haue much Heat, and great and violent deſires and Perturbations, are not ripe for Action, till they haue paſſed the Meridian of their yeares: As it was with Iulius Cæſar, and Septimius Seuerus.”
Variation in an orbit due to the influence of external bodies.