costumier vs designer

costumier and designer both are nouns.

Word	Noun	Adjective	Verb	Adverb
costumier	Yes	No	No	No
designer	Yes	No	No	No

As nouns, designer is a hypernym of costumier; that is, designer is a word with a broader meaning than costumier:

costumier: someone who designs or supplies costumes (as for a play or masquerade)
designer: someone who designs clothing

Other hypernyms of costumier include clothes designer, couturier, fashion designer.

costumier (noun)	designer (noun)
someone who designs or supplies costumes (as for a play or masquerade)	someone who creates plans to be used in making something (such as buildings)
	someone who designs clothing
	a person who specializes in interior design
	a person who devises plots or intrigues
	someone who specializes in graphic design