The definition of appal means to shock or amaze in a negative way.
An example of something that would appal is the sight of someone breaking into your home.
transitive verb-·palled′, -·pal′ling
alt. sp. of appall
(third-person singular simple present appals, present participle appalling, simple past and past participle appalled)
- (UK, less common) Alternative spelling of appall.