environmentalist vs meliorist

environmentalist and meliorist both are nouns.

Word	Noun	Adjective	Verb	Adverb
environmentalist	Yes	No	No	No
meliorist	Yes	No	No	No

As nouns, meliorist is a hypernym of environmentalist; that is, meliorist is a word with a broader meaning than environmentalist:

environmentalist: someone who works to protect the environment from destruction or pollution
meliorist: a disputant who advocates reform

Other hypernyms of environmentalist include crusader, reformer, reformist, social reformer.

environmentalist (noun)	meliorist (noun)
someone who works to protect the environment from destruction or pollution	a disputant who advocates reform