[f. FOSTER sb.1 In OE. *fóstersweoster (Lye). Cf. ON. fóstrsystir.] A female child nursed at the same breast as, or reared together with, another of different parentage.
1649. Jer. Taylor, Gt. Exemp., 37. Scipio Asiaticus … pardoned them at the request of his Foster-sister.
1840. Dickens, Barn. Rudge, xx. [Dolly] had ever since been the humble friend of Miss Haredale, whose foster-sister she was.
