pectus vs male chest

pectus and male chest both are nouns.

Word	Noun	Adjective	Verb	Adverb
pectus	Yes	No	No	No
male chest	Yes	No	No	No

As nouns, male chest is a hyponym of pectus; that is, male chest is a word with a more specific, narrower meaning than pectus:

pectus: the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates
male chest: the chest of a man

Other hyponyms of pectus include bust, female chest.

pectus (noun)	male chest (noun)
the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates	the chest of a man