pecs vs skeletal muscle

pecs and skeletal muscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
pecs	Yes	No	No	No
skeletal muscle	Yes	No	No	No

As nouns, skeletal muscle is a hypernym of pecs; that is, skeletal muscle is a word with a broader meaning than pecs:

pecs: either of two large muscles of the chest
skeletal muscle: a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes

Other hypernyms of pecs include striated muscle.

pecs (noun)	skeletal muscle (noun)
either of two large muscles of the chest	a muscle that is connected at either or both ends to a bone and so move parts of the skeleton; a muscle that is characterized by transverse stripes