ˌBig ˈSisters BrE AmE
a US organization to help girls, especially girls who do not have mothers or who come from families experiencing difficulties. Each girl has her own Big Sister, a woman who meets her regularly to give advice, listen to her problems, play games, and be a ↑ role model . Big Sisters are ↑ volunteer s (=people who work without being paid) , and there is a similar organization for boys called ↑ Big Brothers .