Adjective: horror-stricken 'hor-ur,stri-kun or 'hór-ur,stri-kun [N. Amer], 'hó-ru(r),stri-kun [Brit]- Stricken with horror
"I was horror-stricken at the thought of being late for my interview";
- horrified, horror-struck
See also: afeard [archaic], afeared [archaic], afraid, 'fraid [non-standard]