A more thorough explanation:

filus nullius

Filius nullius is a Latin term that means "son of nobody." It refers to a child who is born out of wedlock and has no legal father. In the past, such children were considered illegitimate and had very few rights.

An example of filius nullius would be a child born to a single mother who does not know the identity of the father. Another example would be a child born to a married woman who has an affair with another man.

These examples illustrate the definition of filius nullius because in both cases, the child does not have a legal father. This means that the child may not have the same rights as a child born to married parents, such as the right to inherit property or receive financial support from a father.