pegleg vs prosthetic device

pegleg and prosthetic device both are nouns.

Word	Noun	Adjective	Verb	Adverb
pegleg	Yes	No	No	No
prosthetic device	Yes	No	No	No

As nouns, prosthetic device is a hypernym of pegleg; that is, prosthetic device is a word with a broader meaning than pegleg:

pegleg: a prosthesis that replaces a missing leg
prosthetic device: corrective consisting of a replacement for a part of the body

Other hypernyms of pegleg include prosthesis.

pegleg (noun)	prosthetic device (noun)
a prosthesis that replaces a missing leg	corrective consisting of a replacement for a part of the body