camp meeting vs group meeting

camp meeting and group meeting both are nouns.

Word	Noun	Adjective	Verb	Adverb
camp meeting	Yes	No	No	No
group meeting	Yes	No	No	No

As nouns, group meeting is a hypernym of camp meeting; that is, group meeting is a word with a broader meaning than camp meeting:

camp meeting: religious (usually evangelistic) meeting held in a large tent or outdoors and lasting several days
group meeting: a formally arranged gathering

Other hypernyms of camp meeting include meeting.

camp meeting (noun)	group meeting (noun)
religious (usually evangelistic) meeting held in a large tent or outdoors and lasting several days	a formally arranged gathering