Green’s Dictionary of Slang

1. (US Und./police) a man who attempts to blackmail a woman who is deceiving her husband.

1859		Matsell Vocabulum 36: ghouls Fellows who watch assignation-houses, and follow females that come out of them to their homes and then threaten to expose them to their husbands, relatives, or friends, if they refuse to give them not only money, but also the use of their bodies.
1927		‘Jargon of the Und.’ in DN V 447: Ghoul, A blackmailer who follows a woman as she leaves an assignation house.

2. a grave robber.

1927		(con. 1878) H. Asbury Gangs of N.Y. 219: Stewart’s body had scarcely been lowered into the grave before rumors were afloat that ghouls planned to steal the corpse and hold it for ransom.
1929		Hall & Niles One Man’s War 38: He began his career as a child beggar and later became a bicycle thief. This was not an overly profitable business, so he turned ghoul, and although grave robbing was a bit messy at times, he made a good living at it.

3. an undertaker.

1900

Bulletin (Sydney) 21 Jul. 11/3: A second advertisement, however, notified that another undertaker would conduct, and that the funeral would start from the hospital at 2.30. The first ghoul won.

4. a morgue attendant.

1903		Bulletin (Sydney) 24 Dec. 21/2: I went to a cemetery, t’other day, to see the last of a friend who had crossed the Great Divide. [...] The ghoul in charge told me that the barbed wire was quite useless unless the flowers were chained down, owing to people coming with telescopic fishing rods in their pockets, and fishing for the vegetables.
1910		Bulletin (Sydney) 7 July 11/1: Last week several of the boss buriers assured Treasurer Watt that the contract ghouls, having once obtained possession of the remains, levied extortionate charges on the relatives and friends, and carried on generally like graveyard wolves.
1912		Bulletin (Sydney) 4 July 13/4: Sundry ghouls – undertakers, monumental masons and the like – lately bought up the remaining allotments in that desirable suburban estate, the Melbourne General Cemetery.

5. an unattractive-looking woman.

1956

I. Shulman Good Deeds Must Be Punished 92: Don’t you mention again the ghouls Phil fixed us up with. [...] Phil must be blind because I’ve seen better heads on pigs.