costumier vs costume designer

costumier and costume designer both are nouns.

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

As nouns, costumier and costume designer are synonyms defined as:

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

Other synonyms of costumier include costumer.

costumier (noun)	costume designer (noun)
someone who designs or supplies costumes (as for a play or masquerade)	someone who designs or supplies costumes (as for a play or masquerade)