group meeting vs assemblage

group meeting and assemblage both are nouns.

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

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

Other hypernyms of group meeting include assembly, gathering.

group meeting (noun)	assemblage (noun)
a formally arranged gathering	the social act of assembling
	a system of components assembled together for a particular purpose
	a group of persons together in one place
	several things grouped together or considered as a whole