flexor muscle vs flexor

flexor muscle and flexor both are nouns.

Word	Noun	Adjective	Verb	Adverb
flexor muscle	Yes	No	No	No
flexor	Yes	No	No	No

As nouns, flexor muscle and flexor are synonyms defined as:

flexor muscle and flexor: a skeletal muscle whose contraction bends a joint

flexor muscle (noun)	flexor (noun)
a skeletal muscle whose contraction bends a joint	a skeletal muscle whose contraction bends a joint