welcome party for new students or club members
Campus slang; short for 新入生歓迎コンパ. Used mainly in university club contexts.
Are you going to the welcome party for new students next week?
I talked with many new students at the club's welcome party.
Abbreviation of 新入生歓迎コンパ (shinnyūsei kangei konpa), where 新歓 is a contraction of 新入生歓迎 and コンパ comes from German 'Kompanie' or English 'company', meaning a social gathering.