group meeting vs assembly

group meeting and assembly both are nouns.

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

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

Other hypernyms of group meeting include assemblage, gathering.

group meeting (noun)	assembly (noun)
a formally arranged gathering	the social act of assembling
	the act of constructing something (as a piece of machinery)
	a group of machine parts that fit together to form a self-contained unit
	a public facility to meet for open discussion
	a unit consisting of components that have been fitted together
	a group of persons who are gathered together for a common purpose