The term 'Frequent Joiner' is used to describe someone who often joins in on activities or events. This person is usually seen as a social butterfly, AND is often the life of the party. The crossword solutions for this term are 'REP' AND 'REG'. The acronym 'REP' stands for 'regularly attending person', while 'REG' stands for 'regularly engaging guest'. Both terms refer to someone who is a frequent joiner.