masquerade ball vs fancy-dress ball

masquerade ball and fancy-dress ball both are nouns.

Word	Noun	Adjective	Verb	Adverb
masquerade ball	Yes	No	No	No
fancy-dress ball	Yes	No	No	No

As nouns, masquerade ball and fancy-dress ball are synonyms defined as:

masquerade ball and fancy-dress ball: a ball at which guests wear costumes and masks

Other synonyms of masquerade ball include masked ball.

masquerade ball (noun)	fancy-dress ball (noun)
a ball at which guests wear costumes and masks	a ball at which guests wear costumes and masks