ˌBig ˈSisters
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 volunteers (=people who work without being paid), and there is a similar organization for boys called Big Brothers.

[TahlilGaran] Dictionary of Contemporary English ▲