mixed drink vs highball

mixed drink and highball both are nouns.

Word	Noun	Adjective	Verb	Adverb
mixed drink	Yes	No	No	No
highball	Yes	No	No	No

As nouns, highball is a hyponym of mixed drink; that is, highball is a word with a more specific, narrower meaning than mixed drink:

mixed drink: made of two or more ingredients
highball: a mixed drink made of alcoholic liquor mixed with water or a carbonated beverage and served in a tall glass

mixed drink (noun)	highball (noun)
made of two or more ingredients	a mixed drink made of alcoholic liquor mixed with water or a carbonated beverage and served in a tall glass