acrocephaly vs birth defect

acrocephaly and birth defect both are nouns.

Word	Noun	Adjective	Verb	Adverb
acrocephaly	Yes	No	No	No
birth defect	Yes	No	No	No

As nouns, birth defect is a hypernym of acrocephaly; that is, birth defect is a word with a broader meaning than acrocephaly:

acrocephaly: a congenital abnormality of the skull; the top of the skull assumes a cone shape
birth defect: a defect that is present at birth

acrocephaly (noun)	birth defect (noun)
a congenital abnormality of the skull; the top of the skull assumes a cone shape	a defect that is present at birth