luncheon party; lunch meeting
A formal or organized lunch gathering, often for business or social purposes. The kanji 午餐 is somewhat formal and may be replaced by 昼食 in casual settings.
A luncheon party for new employees will be held next week.
At the luncheon, I spoke with an important client.
Compound of 午餐 (gosan, 'lunch', from Middle Chinese) and 会 (kai, 'meeting, party'). The reading ごさん for 午餐 is the on'yomi. The term is relatively modern and formal.