big sister

American  

noun

1. an elder sister.

2. (sometimes initial capital letters) a woman who individually or as a member of an organized group undertakes to sponsor or assist a girl in need of help or guidance.

3. (sometimes initial capital letters) a young woman in the junior or senior class in college who advises a young woman in the freshman class on studies, social activities, etc., often as a part of a sorority program.

---

Example Sentences

"I loved her to bits, she was my big sister who did everything for all of us."

From BBC • Mar. 10, 2026

What she found was that the relationship went beyond business; she sees her agent as part negotiator, part therapist, part big sister.

From The Wall Street Journal • Mar. 4, 2026

Affectionately called "big sister" by her teammates, she is leading a new generation of Japanese stars including Nakai, 17, and Chiba, 20.

From Barron's • Feb. 17, 2026

Kara was like a big sister to me — really helping me find myself and listening to me.

From Los Angeles Times • Aug. 26, 2025

Jinjoo craned her neck and was shocked to recognize her gomo, her father’s big sister.

From "Finding Junie Kim" by Ellen Oh