A Magic Deficient Human is a human born to at least one magical parent, but is incapable of performing magic — the opposite of wizard born from a Non-Magic Human. They are also called wizard-born, similar to terms such as Muggleborn or No-Maj-Born, though this is less common. There is no true universal term for Magic Deficient Humans, as each wizarding community in each country has different terms for them.
Notably, wizards born to non-magic parents are descended from Magic Deficient Humans.
Magic Deficient Human terms
The Commonwealth of Australia
In Australia, a Magic Deficient Human is referred to as a "Drongo". The plural form is "Drongos".
The United Kingdom of Great Britain and Northern Ireland
In the United Kingdom, a Magic Deficient Human is referred to as a "Squib", with "Squibs" being plural. It is uknown when the term originated. Squibs are commonly looked down upon in the Wizarding community by pure-bloods, and regarded even by half-bloods with pity. The term can also be used as an insult towards a witch or wizard whose skill in magic is believed to be subpar.
- Squib on Harry Potter Wiki