- an elder sister.
- (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.
- (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.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for big sister
"Well, you must come if you ever care to," she said, with a big-sister graciousness.Ramsey Milholland
Libby smiled in an amused, big-sister sort of way, asking how Will'm supposed anybody could read his letters.Miss Santa Claus of the Pullman
Annie Fellows Johnston
As she looked at the young and slender girl before her, a big-sister feeling came sweeping over her.The Crystal Ball
Roy J. Snell
She was shy of the big-sister manner; Vida would either laugh at her or snatch the idea and change it to suit herself.Main Street