pompousness vs ostentation

pompousness and ostentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
pompousness	Yes	No	No	No
ostentation	Yes	No	No	No

As nouns, pompousness and ostentation are synonyms defined as:

pompousness and ostentation: lack of elegance as a consequence of being pompous and puffed up with vanity

Other synonyms of pompousness include inflation, ostentatiousness, pomposity, pretentiousness, puffiness, splashiness.

pompousness (noun)	ostentation (noun)
lack of elegance as a consequence of being pompous and puffed up with vanity	pretentious or showy or vulgar display
	lack of elegance as a consequence of being pompous and puffed up with vanity
	a gaudy outward display