Imagine a couple of snakes getting loose in a pet shop, and the manager running around trying to round up the snakes and calm down the customers, and you'll picture a perturbed person. Perturbed means flustered and confused.
When you're perturbed, you're upset by something, and rattled enough by it to be thrown off your usual calmness into a state of confusion. In astronomy, perturbation is defined as "the effects on a large body when it is subjected to gravitational effects from more than one other large body." When a planet is perturbed in astronomy, it is pulled in different directions by strong forces, which is a great metaphor for what happens to a person who is perturbed.
