per‧tur‧ba‧tion /ˌpɜːtəˈbeɪʃən $ ˌpɜːrtər-/ 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

[TahlilGaran] Dictionary of Contemporary English ▲