megrim vs headache

megrim and headache both are nouns.

Word	Noun	Adjective	Verb	Adverb
megrim	Yes	No	No	No
headache	Yes	No	No	No

As nouns, headache is a hypernym of megrim; that is, headache is a word with a broader meaning than megrim:

megrim: a severe recurring vascular headache; occurs more frequently in women than men
headache: pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs

Other hypernyms of megrim include cephalalgia, head ache.

megrim (noun)	headache (noun)
a severe recurring vascular headache; occurs more frequently in women than men	something or someone that causes anxiety; a source of unhappiness
	pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs