A ghoul is a folkloric monster

Monster

A monster is any fictional creature, usually found in legends or horror fiction, that is somewhat hideous and may produce physical harm or mental fear by either its appearance or its actions...

 associated with graveyards and consuming human flesh, often classified as undead

Undead

Undead is a collective name for fictional, mythological, or legendary beings that are deceased and yet behave as if alive. Undead may be incorporeal, such as ghosts, or corporeal, such as vampires and zombies...

. The oldest surviving literature that mention ghouls is likely One Thousand and One Nights. The term is first attested in English in 1786, in William Beckford

William Beckford

William Beckford may refer to:* William Beckford , English businessman, often called "Alderman Beckford", father of William Thomas* William Beckford of Somerley , Jamaican slave-owner and writer...

's Orientalist

Orientalism

Orientalism is a term used for the imitation or depiction of aspects of Eastern cultures in the West by writers, designers and artists, as well as having other meanings...

 novel Vathek

Vathek

Vathek is a Gothic novel written by William Beckford...

, which describes the ghūl of Arabian folklore.

By extension, the word ghoul is also used derogatorily to refer to a person who delights in the macabre

Macabre

In works of art, macabre is the quality of having a grim or ghastly atmosphere. Macabre works emphasize the details and symbols of death....

.
Ghoul is from the Arabic ghul, from ghala 'to seize'.