Bull vs doer

Bull and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
Bull	Yes	No	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of Bull; that is, doer is a word with a broader meaning than Bull:

Other hypernyms of Bull include actor, worker.

Bull (noun)	doer (noun)
the second sign of the zodiac; the sun is in this sign from about April 20 to May 20	a person who acts and gets things done
(astrology) a person who is born while the sun is in Taurus