It really isn’t quite that simple. There are Intersex people who have ambiguous genitalia and there are several viable chromosome combos besides XX and XY.
In humans syndromes that lead to ambiguous (“intersex”) presentation and/or chromosomes are still operating in a binary system, eh Klinefelter affects boys.
The same is true for (very) rare hermaphroditism: in this case both gametes could in theory be produced, in practice though individuals are sterile.
Chromosomal abnormalities would be the modern term, it applies to both sexual as well as other chromosomal abnormalities like Down.
But to answer the question as asked: Yes, it fulfills the definition of the older term.
> Is it a birth defect?