Squib

"A Squib is someone who was born into a wizarding family but hasn’t got any magic powers. Kind of the opposite of Muggle-born wizards, but Squibs are quite unusual."

- Ron Weasley discussing Argus Filch

A Squib is a non-magical person who is born to at least one magical parent. Squibs are, in essence, the antithesis of Muggle-born wizards and witches. They are rare and are looked upon with some degree of disdain by some witches and wizards, particularly pure-bloods. J. K. Rowling has stated that Muggle-born witches and wizards are descended from Squibs who married Muggles; the magical gene resurfaces after many generations unexpectedly.

Along with contrasting Squibs with muggle-borns, they should also be contrasted with the muggle parents of muggle-born witches and wizards. Muggle parents are simply muggles who just happen to know about the magical world, but, seeing as they were not born to magical parents, they are not squibs.

Differences between Squibs and Muggles
In addition to being born into magical rather than Muggle families, Squibs are different from Muggles in that they notice and comprehend the wizarding world. They are able to see Hogwarts, as it would be very hard for Filch to work there if he could not see it. They also have access to certain magical objects and creatures that can help them. Argus Filch as well as Arabella Figg have formed wizarding-like relationships with cats that, in the case of the latter, have been cross-bred with Kneazles.

Attitude toward Squibs
"You disgusting little Squib, you filthy little blood traitor!"

- Marvolo Gaunt to his daughter, whom he believed to be a Squib.

The Ministry of Magic does not keep records of Squib births, a sign of wizard society's general disregard for them. Although they can check if said person is a squib using their parent's names as demonstrated in Harry Potter and the Order of the Phoenix during the hearing of Harry Potter. The common practice with Squibs is to send them off to Muggle schools as children and encourage them to integrate with the Muggle community, which is much kinder than letting them live in the magical world where they will always be treated as second-class citizens. Some, however, choose to remain in the wizarding world regardless. Some pure-blood families, such as the Blacks, disown any Squib members and remove them from their family trees as they removed Marius Black.

Even families that are tolerant of Muggles and Muggle-borns seem to regard Squibs poorly. For example, the Weasley family seems embarrassed to have a Squib who works in the Muggle world as an accountant in the family. Also, many wizarding families are anxious to see early signs of magical ability and are upset by the prospect that a member might be a Squib. Neville Longbottom and Merope Gaunt were both thought to be Squibs by their relatives because of this, though ultimately both of them were magical. However, the wizarding world did set up at least one organisation to support Squibs, called Society for the Support of Squibs.

It is unclear as to Lord Voldemort's attitude towards Squibs. He had personally noted throughout his life that he aims to purge Muggle-born wizards and witches for "stealing" magic. However, as Argus Filch was allowed to remain in Hogwarts, it is likely they weren't prosecuted as blood traitors.

Known Squibs

 * Arabella Figg
 * Argus Filch
 * J. K. Rowling
 * Marius Black
 * The Thurkell brothers

Believed Squibs

 * Neville Longbottom — discovered to not be a Squib when his Uncle Algie 'accidentally' dropped him out of a window and he bounced down the road.
 * Merope Gaunt — discovered not to be a Squib when she married Tom Riddle Sr. after running away from home. She was able to develop her magical abilities freely as she had not displayed them before due to fear of her father and brother.
 * Ariana Dumbledore — unable to control her magic after being traumatised by an attack by Muggle boys, and kept hidden by her family.
 * Unnamed second cousin of Molly Weasley (assumed)

Behind the scenes

 * The term likely comes from the English expression "a damp squib" (dud firecracker), an expected delight that disappoints.
 * The Star Wars series also uses the term Squib as the name of an alien species.
 * Idris Oakby, founder of the Society for the Support of Squibs, may have been a Squib herself.
 * Two squibs (both are minor characters) seen in the series are Arabella Figg and Argus Filch. Both seem to love cats and have the same initials.