hummer vs vocalist

hummer and vocalist both are nouns.

Word	Noun	Adjective	Verb	Adverb
hummer	Yes	No	No	No
vocalist	Yes	No	No	No

As nouns, vocalist is a hypernym of hummer; that is, vocalist is a word with a broader meaning than hummer:

hummer: a singer who produces a tune without opening the lips or forming words
vocalist: a person who sings

Other hypernyms of hummer include singer, vocaliser, vocalizer.

hummer (noun)	vocalist (noun)
(baseball) a pitch thrown with maximum velocity	a person who sings
a singer who produces a tune without opening the lips or forming words