general practitioner vs MD

general practitioner and MD both are nouns.

Word	Noun	Adjective	Verb	Adverb
general practitioner	Yes	No	No	No
MD	Yes	No	No	No

As nouns, MD is a hypernym of general practitioner; that is, MD is a word with a broader meaning than general practitioner:

general practitioner: a physician who is not a specialist but treats all illnesses
MD: a licensed medical practitioner

Other hypernyms of general practitioner include doc, doctor, Dr., medico, physician.

general practitioner (noun)	MD (noun)
a physician who is not a specialist but treats all illnesses	a doctor's degree in medicine
	a Mid-Atlantic state; one of the original 13 colonies, with capital Annapolis
	a licensed medical practitioner