1. thirdborn - Noun
2. thirdborn - Adjective
Born as the third child to parent or family.
Mary, the thirdborn Bennett child in the novel Pride and Prejudice, receives the least attention.
Third of a particular type to be born to a parent or family.
Prince Arthur was Queen Victoria's thirdborn son and her seventh child overall.
thirdborn (plural thirdborns)
The third child born to a parent or family.