1. Causing consternation
   "appalling conditions";
   - dismaying

1. An experience that appals
   "is it better to view the appalling or merely hear of it?"

1. Strike with disgust or revulsion
   "The scandalous behaviour of this married woman appalled her friends";
   - shock, offend, scandalize, scandalise [Brit], appall [US], outrage
    
2. Fill with apprehension or alarm; cause to be unpleasantly surprised
   "I was appalled at the thought of being late for my interview";
   - dismay, alarm, appall [US], horrify

See also: alarming

Type of: affright, disgust, experience, fright [archaic], frighten, nauseate, revolt, scare, sicken