househusband vs hubby

househusband and hubby both are nouns.

Word	Noun	Adjective	Verb	Adverb
househusband	Yes	No	No	No
hubby	Yes	No	No	No

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

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

Other hypernyms of househusband include husband, married man.

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