mesne lord vs nobleman

mesne lord and nobleman both are nouns.

Word	Noun	Adjective	Verb	Adverb
mesne lord	Yes	No	No	No
nobleman	Yes	No	No	No

As nouns, nobleman is a hypernym of mesne lord; that is, nobleman is a word with a broader meaning than mesne lord:

mesne lord: a feudal lord who was lord to his own tenants on land held from a superior lord
nobleman: a titled peer of the realm

Other hypernyms of mesne lord include Lord, noble.

mesne lord (noun)	nobleman (noun)
a feudal lord who was lord to his own tenants on land held from a superior lord	a titled peer of the realm