perturber

Noun

 * 1) One who or that which perturbs.
 * 2)  A source of perturbation.
 * This moon is a significant perturber.
 * This moon is a significant perturber.

Related terms

 * perturb
 * perturbation

Etymology
.

Verb

 * 1)  to disrupt, to disturb
 * 2)  to throw off, to fluster