costume designer vs designer

costume designer and designer both are nouns.

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

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

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

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

costume designer (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