ghastly

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Causing shock, revulsion, or horror; terrifying.
• adjective Resembling a ghost; pale or pallid.
• adjective Extremely unpleasant or bad.

from The Century Dictionary.

• In a ghastly manner; dreadfully; hideously; with a deathlike aspect.
• Dreadful or deathly in aspect or look; deathlike; haggard; shocking.
• Deathly in import or suggestion; morally dreadful or shocking.
• Synonyms Ghastly, Grim, Grisly, Haggard, Hideous; pale, wan, cadaverous, frightful. Hideous may apply to sound, as a hideous noise; the others not. All in modern use apply primarily to sight and secondarily to mental perception, except haggard, which connotes sight only. Ghastly, as it is most commonly used, means deathly pale, deathlike, referring to the countenance, but its signification has been extended to denote anything that is suggestive of death, or even repulsive and shocking, as Milton's “mangled with ghastly wounds” (P. L., vi. 368), “a ghastly smile” (Milton, P. L., ii. 846), a ghastly jest. Grim characterizes a rigid cast of countenance, indicating a severe, stern, or even ruthless disposition. Grisly refers to the whole form or aspect, especially when dark, forbidding, or such as to inspire terror. Haggard adds to the idea of paleness of countenance that of being wasted by famine or protracted mental agony. Hideous, used of looks, applies to the whole form or scene, and means simply repulsive, extremely unpleasant to see: as, hideous features; a hideous scene. See pale.

from the GNU version of the Collaborative International Dictionary of English.

• adverb In a ghastly manner; hideously.
• adjective Like a ghost in appearance; deathlike; pale; pallid; dismal.
• adjective Horrible; shocking; dreadful; hideous.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Horrifyingly shocking.
• adjective Extremely bad.
• adverb In a ghastly manner.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective shockingly repellent; inspiring horror
• adjective gruesomely indicative of death or the dead