pacifist vs peacenik

pacifist and peacenik both are nouns.

Word	Noun	Adjective	Verb	Adverb
pacifist	Yes	Yes	No	No
peacenik	Yes	No	No	No

As nouns, peacenik is a hyponym of pacifist; that is, peacenik is a word with a more specific, narrower meaning than pacifist:

pacifist: someone opposed to violence as a means of settling disputes
peacenik: someone who prefers negotiations to armed conflict in the conduct of foreign relations

Other hyponyms of pacifist include dove.

pacifist (noun)	peacenik (noun)
someone opposed to violence as a means of settling disputes	someone who prefers negotiations to armed conflict in the conduct of foreign relations

pacifist (adjective)	peacenik (adjective)
opposed to war