/ ˌpɜːtəˈbeɪʃn; NAmE ˌpɜːrtərˈb-/ noun
1.
[ U ] ( formal ) the state of feeling anxious about sth that has happened
SYN alarm
2.
[ C , U ] ( technical ) a small change in the quality, behaviour or movement of sth :
temperature perturbations
••
WORD ORIGIN
late Middle English : from Latin perturbatio(n-) , from the verb perturbare disturb greatly, from per- completely + turbare disturb.