lunch meeting vs luncheon meeting

lunch meeting and luncheon meeting both are nouns.

Word	Noun	Adjective	Verb	Adverb
lunch meeting	Yes	No	No	No
luncheon meeting	Yes	No	No	No

As nouns, lunch meeting and luncheon meeting are synonyms defined as:

lunch meeting and luncheon meeting: a meeting for lunch; usually to conduct business while eating

lunch meeting (noun)	luncheon meeting (noun)
a meeting for lunch; usually to conduct business while eating	a meeting for lunch; usually to conduct business while eating