blackball vs ostracise

blackball is a noun but ostracise is not a noun.

Word	Noun	Adjective	Verb	Adverb
blackball	Yes	No	Yes	No
ostracise	No	No	Yes	No

As verbs, blackball and ostracise are synonyms defined as:

Other synonyms of blackball include ban, banish, cast out, ostracize, shun.

blackball (noun)	ostracise (noun)
the act of excluding someone by a negative vote or veto

blackball (verb)	ostracise (verb)
expel from a community or group	avoid speaking to or dealing with
vote against; refuse to endorse; refuse to assent	expel from a community or group