meconium vs faecal matter

meconium and faecal matter both are nouns.

Word	Noun	Adjective	Verb	Adverb
meconium	Yes	No	No	No
faecal matter	Yes	No	No	No

As nouns, faecal matter is a hypernym of meconium; that is, faecal matter is a word with a broader meaning than meconium:

meconium: thick dark green mucoid material that is the first feces of a newborn child
faecal matter: solid excretory product evacuated from the bowels

Other hypernyms of meconium include BM, dejection, faeces, fecal matter, feces, ordure, stool.

meconium (noun)	faecal matter (noun)
thick dark green mucoid material that is the first feces of a newborn child	solid excretory product evacuated from the bowels