U3A stands for University of the Third Age.
The term third age means no longer in full time work. U3A provides opportunities for people to meet, share experiences and pursue commonly held interests. The club meets monthly with a guest speaker with unique experience in their field. Interest (study) groups meet at other times and it is encouraged that members belong to at least one study group. Examples could be Art, Music, Literature, Film, History etc. So if you are perhaps retired and want to learn more or you have a particular skill, knowledge and experience to share then this is for you.
The national organisation U3A.nz has information on all U3A clubs in New Zealand.