househusband vs married man

househusband and married man both are nouns.

Word	Noun	Adjective	Verb	Adverb
househusband	Yes	No	No	No
married man	Yes	No	No	No

As nouns, married man is a hypernym of househusband; that is, married man is a word with a broader meaning than househusband:

househusband: a husband who keeps house while his wife earns the family income
married man: a married man; a woman's partner in marriage

Other hypernyms of househusband include hubby, husband.

househusband (noun)	married man (noun)
a husband who keeps house while his wife earns the family income	a married man; a woman's partner in marriage