per ‧ tur ‧ ba ‧ tion /ˌpɜːtəˈbeɪʃ ə n $ ˌpɜːrtər-/ BrE AmE noun
1 . [uncountable and countable] technical a small change in the movement, quality, or behaviour of something:
climatic perturbations
2 . [uncountable] formal worry about something that has happened or will happen