ghastly

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Inspiring shock, revulsion, or horror by or as if by suggesting death; terrifying: a ghastly murder.
2. adj. Suggestive of or resembling ghosts.
3. adj. Extremely unpleasant or bad: "in the most abominable passage of his ghastly little book” ( Conor Cruise O'Brien).
4. adj. Very serious or great: a ghastly error.

Century Dictionary and Cyclopedia

1. Dreadful or deathly in aspect or look; deathlike; haggard; shocking.
2. Deathly in import or suggestion; morally dreadful or shocking.
3. 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.
4. In a ghastly manner; dreadfully; hideously; with a deathlike aspect.

Wiktionary

1. adj. Horrifyingly shocking.
2. adj. Extremely bad.
3. adv. In a ghastly manner.

GNU Webster's 1913

1. adj. Like a ghost in appearance; deathlike; pale; pallid; dismal.
2. adj. Horrible; shocking; dreadful; hideous.
3. adv. In a ghastly manner; hideously.

WordNet 3.0

1. adj. shockingly repellent; inspiring horror
2. adj. gruesomely indicative of death or the dead