SPECIES INFORMATION
EYE COLOUR
Varies
SKIN COLOUR
Varies
HAIR COLOUR
Varies
RELATED TO
Wizardkind
Muggles
HEIGHT OF AVERAGE ADULT
Varies
MORTALITY
Mortal
DISTINCTION
Wizarding parentage but cannot use magic
AFFILIATION
Wizardkind
Muggles
MINISTRY OF MAGIC CLASSIFICATION
Being
STATUS
Extant
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.
BASIC DESCRIPTION OF A SQUIB
A Squib, also known as a wizard-born, is a non-magical person who is born to at least one magical parent. 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 many generations later.
Overview
A Squib is a human who is born with at least one magical parent, but does not inherit magic from said parent. A wizard or witch child would typically show signs of magical abilities at seven years old; any such child who does not is leaning on being a Squib (though they are possibly late-bloomers).
Squibs are rare, even just one being born into a family. This is why the case of Thaddeus Thurkell's seven Squib sons is particularly noteworthy.
Squibs are incapable of practising magic in any way, as Argus Filch found out when he attempted to use the supplementary course Kwikspell, which was designed to improve inadequate wizarding skills, to no effect as he had no magical skills to improve upon.
History
In the 1600s, Isolt Sayre, the famous founder of Ilvermorny School of Witchcraft and Wizardry, gave birth to a daughter whom she named Martha. Martha was named after her paternal grandmother and while her twin sister Rionach was magical, Martha was not. Martha was the only one in the family to be born a Squib, and because of that she considered her upbringing at Ilvermorny to be painful. Martha went on to marry and lived as a No-Maj.
In 1858 Angus Buchanan never received a Hogwarts acceptance letter, but got as far as the Sorting Hat, before he was exposed as a Squib. In sheer desperation, he threw himself ahead of a girl whose name had been called and placed the Hat upon his head. The horror of the moment when the Hat announced kindly that the boy beneath it was a good-hearted chap, but no wizard, would never be forgotten by those who witnessed it. Angus took off the hat and left the hall with tears streaming down his face. This had never happened before and it has never happened since. Angus being a Squib caused him to become estranged from his family.
In 1900, Angus wrote an inspirational book, titled My Life as a Squib. His book helped break the taboos of Squib culture in wizarding society. Angus ended up becoming a star in the Muggle sport of Scottish rugby, and his sporting talents became so well known that wizarding kind fell in love with his inspirational story, not to mention developing an odd interest in rugby.
While Eugenia Jenkins was Minister for Magic from 1968 to 1975, Squib Rights marches began to surface. However, these marches attracted pure-blood riots.
Different from 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: 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.
Despite the differences between Squibs and Muggles they usually have a stronger affinity with each other than with wizards. For obvious reasons, Squibs usually lead Muggle lifestyles, and are known to be sent to Muggle schools. Some voluntarily choose to cut themselves off from the wizarding world altogether. Isolt Sayre's Squib daughter Martha chose to distance herself from magic entirely. Others live as allies to wizardkind and others, living somewhere in the middle, choose to work with wizards but are not very neighbourly to them.
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 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 Orford Umbridge, an unenthusiastic wizard who was tolerant enough to marry a Muggle woman, would come to despise his son for being a Squib. John Buchanan, proud of his wizarding ancestry, came to loathe his son for being a squib and violently disowned him, even forbidding his other ten children from seeing him again.
Even families that are tolerant of Muggles and Muggle-borns seem to regard Squibs poorly. 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. Some magical families would often blame any Muggle parents for a Squib's birth, as Orford Umbridge and his witch daughter would blame his Muggle wife, Ellen Cracknell, for being the fault of the son being born a Squib. However, the wizarding world did set up at least one organisation to support Squibs, called Society for the Support of Squibs. Karl Jenkins rudely called Albus Potter "Slytherin Squib" due to his demonstration of poor magical skills in his first year at Hogwarts.
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.
Because of their low statuses in the magical community, any Squibs who chose to remain in the Wizarding world may develop a bitter personality towards witches and wizards. Argus Filch, in particular, was rather unpleasant with most students and would be rather harsh on them; Ron Weasley believed that Filch's Squib status may be the cause of this attitude. Martha Steward II found it very painful in living among magical folks that she eventually severed ties with the community to assimilate into Muggle society.
Squibs, at times, tried to fight for their rights, as they marched for equality in around 1968 or 1969. However, pure-blood extremists would absolutely refuse to give anything respectful towards Squibs, and even launched an attack against the marchers that led to riots. Even in the 1990s, the Ministry refused to keep track of Squib births, showing a disregard for Squibs' attempt to earn their rights.
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.
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.
It is unknown what the term would be for the non-magical offspring of a Squib and a Muggle.
Mafalda, a deleted character, was set to be the child of a possible Squib and a Muggle. However since the character was cut this information has yet to be confirmed.