Meaning of “appal” - Learner’s Dictionary

appal

verb [ T ] (present participle appalling, past tense and past participle appalled) UK (US appall) uk us /əˈpɔːl/

to make someone extremely shocked or upset:

The amount of violence on television appals me.
We were appalled at/by her behaviour.
appalled adjective

(Definition of “appal” from the Cambridge Learner’s Dictionary © Cambridge University Press)