Definition
The preserved remains of a body, human or animal, from which fluids have been removed. Although mummification can occur through natural processes in very dry conditions, the most common conception of a mummy is that of one deliberately embalmed as a preparation for burial, for which additional preservative measures have been performed. In ancient Egypt, mummification was performed on the bodies of humans and of cats, and was considered a necessary step in preparing the deceased for the afterlife.
It is unclear whether the type of mummy Parvati Patil fears (which the boggart impersonated during her first Defence Against the Dark Arts lesson with Remus Lupin, PA7), is an actual mummy animated or some Dark Creature resembling a mummy. If the latter is the case, a mummy is a frightening creature, bandaged, bloody, and sightless, possibly a manifestation of a curse left behind by ancient wizards (PA7). (Of course, if Parvati was exposed to Muggle entertainment as a child, she may just have watched too many horror movies.)
Commentary
Notes
Prisoner of Azkaban has a great deal of Egyptian symbolism including Parvati and her Mummy. There is also the fact that the Weasleys just visited Egypt where Ron's brother Bill is a curse-breaker for Gringotts Bank. Harry's godfather has the name Sirius, named for the "dog star" worshipped by Egyptians as the god Osiris. He also rules the "underworld" as Sirius keeps rising out of tunnels under the school, and finally pulling Ron under the Whomping Willow. The vulture hat on the Gran-Snape boggart represents the mother-goddess Mut, protective because the vulture had wide wings to surround their young on the nest and a big shadow as it flew over the desert. Cleopatra and King Tut both wore headdresses with vulture and snake motifs to represent their rule over northern and southern Egypt ~ SIP Source: Discover Egypt: Ancient Gods and Goddesses