To perturb is to bug or bother someone by confusing them or throwing them off balance. You can try, but it's almost impossible to perturb the guards outside Buckingham Palace.
If you're having trouble getting used to the word perturb, you're in luck! It's similar in meaning to the verb "disturb." That's right, to perturb is to disturb, but in a way that suggests you're throwing it off its usual path or routine. The movie Born Free truly perturbed widespread views about animals—people suddenly started seeing them as individuals. If you stare at a person you don't know, it won't be long before you perturb them.