hideous, dread, horrid, sickening, macabre, dire, terrific, unspeakable, fearful, appalling, frightful, scandalous, outrageous, nightmare, terrible, abominable, slimy, forbidding, hair-raising, redoubtable, scary, painful, taboo, direful, surly, ghastly, nightmarish, tremendous, grisly, lurid, monstrous, vile, shocking, horrific, gruesome, revolting, fearsome, spine-chilling, unworthy, disgusting, grievous, despicable, atrocious, indecent, awful, wretched, ugly, repulsive, dreadful, formidable, horrible, worthless, horrendous, detestable, flagitious
frightening (part of speech: verb)
haunting (part of speech: verb)
- It peered into the immense caverns of a cloud to which it had returned, illuminating to us unsuspected and horrifying possibilities of hiding- places above us. - "Waiting for Daylight", Henry Major Tomlinson.
- Recent examination of school children in various cities in England and America has revealed a state of physical ill- being most deplorable in the present, and horrifying to contemplate for its future results. - "The Cost of Shelter", Ellen H. Richards.
- It was a horrifying experience. - "That Little Girl of Miss Eliza’s", Jean K. Baird.