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 magical parents. Squibs are, in essence, 'wizard-born Muggles.' They are rare and are looked upon with a degree of disdain by some witches and wizards, particularly pure-bloods. Muggle-born witches and wizards are descended from Squibs who married Muggles; the magical ability unexpectedly resurfaces after many generations.

Differences between Squibs and Muggles
In addition to being born into magical rather than Muggle families, Squibs are different from Muggles by their knowledge of the wizarding world. They are able to see things that are hidden from the Muggles and 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.

Squibs should also be contrasted with the Muggle relatives of witches and wizards. Muggle parents, siblings, spouses etc. are simply Muggles who happen to know about the magical world.

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. They can, however, check if a person is a squib using their parents' names, as demonstrated in 1995 during the disciplinary hearing of Harry Potter. The common practise 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 was thought to be a Squib by his relatives because of this, though he proved to be magical. Similarly, Merope Gaunt was called a Squib by her father Marvolo as a slur, due to her poor magical abilities, inhibited by her fear of her father and brother. 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 were not prosecuted as blood traitors.

Known Squibs

 * Arabella Figg
 * Argus Filch
 * 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.
 * Ariana Dumbledore — unable to control her magic after being traumatised by an attack by Muggle boys, and kept hidden by her family. Neighbours believe Kendra Dumbledore to be ashamed of her daughter and spread rumours that Ariana was locked in the cellar due to her being a Squib when in fact it was her powers that had gone awry.
 * Unnamed second cousin of Molly Weasley — assumed to be a Squib due to working as an accountant in the Muggle world. Whether he is an actual Squib or not has yet to be confirmed.

Behind the scenes

 * The term likely comes from the English expression "a damp squib" (dud firecracker), an expected delight that disappoints.
 * The word squib also refers to an incomplete or insufficient discharge of a firearm.
 * The word could also be a pun on "skip", referring to the fact that the person was "skipped" by magic. In fact, at least one book series (Terry Goodkind's  The Sword of Truth) used the word in a meaning analogous to squib in several books.
 * 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.
 * Even though Merope Gaunt had proven she is capable at magic, her father derogatorily referred her as a Squib due to her poor control. Whether he believed her to be an actual Squib or that he was simply insulting her is unclear.

Appearances

 * Harry Potter and the Philosopher's Stone
 * Harry Potter and the Philosopher's Stone (film)
 * Harry Potter and the Philosopher's Stone (video game)
 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Chamber of Secrets (video game)
 * Harry Potter and the Prisoner of Azkaban
 * Harry Potter and the Prisoner of Azkaban (film)
 * Harry Potter and the Prisoner of Azkaban (video game)
 * Harry Potter and the Goblet of Fire
 * Harry Potter and the Goblet of Fire (film)
 * Harry Potter and the Goblet of Fire (video game)
 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Order of the Phoenix (film)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (film)
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Harry Potter and the Deathly Hallows: Part 1 (video game)
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * LEGO Harry Potter: Building the Magical World
 * LEGO Harry Potter: Characters of the Magical World
 * LEGO Harry Potter: Years 1-4
 * LEGO Harry Potter: Years 5-7
 * J. K. Rowling Official Site
 * Harry Potter LEGO Sets