In casual use, especially when the topic is Halloween or horror movies, ghastly and ghoulish get lumped together, along with other grisly, gory, and gruesome words beginning with the letter “g.” Ghastly and ghoulish have the definitions “like a ghost” and “like a ghoul,” but it’s the extended meanings we’re concerned with here. Ghastly, often used of acts and events, suggests something shockingly frightful, horrible, or repellent, particularly to the eye. You can be sure a ghastly accident or ghastly murder involved a fair amount of blood and gore. Ghoulish is less frequent, as ghouls are less prominent in American culture than ghosts. A ghoul is a demon originating in Muslim lore, said to dig up graves and feed on human corpses, and ghoulish suggests something that demonstrates monstrous cruelty or a fascination with such: the zombies’ ghoulish mission; ghoulish fascination with serial killer movies.
Clothing refers to what we cover our bodies with. If we’re talking about clothing and specify that it is worn by a certain group of people or for a particular occasion, garb could be a strong alternative: prison garb; funeral garb. Garb sometimes suggests costume: actors dressed in period garb. Perhaps because garb draws attention to itself separately from the wearer, it is used figuratively, as the word “guise” is, to refer to an outward appearance that hides what’s underneath: manipulation cloaked in the garb of generosity.
Both verbs refer to the action of internal forces that push or urge people to do something. Drive suggests the powerful effect of these forces, typically passion, need, fear, or desire, on a person’s actions or choices, where the action becomes almost involuntary: driven by a desire for conquest. Impel comes from the Latin word that means “to strike against; to set in motion,” and can mean literally “to push forward” as wind impels a ship. More frequently, impel is used figuratively, and suggests an urging forward towards action by something less compulsory than drive suggests and more of an internal motive or incentive.