Pronunciation: (sis'tur),[key] —n. 1. a female offspring having both parents in common with another offspring; female sibling.
2. Also called half sister. a female offspring having only one parent in common with another offspring.
4. a female friend or protector regarded as a sister.
5. a thing regarded as feminine and associated as if by kinship with something else: The ships are sisters. 6. a female fellow member, as of a church.
7. a female member of a religious community that observes the simple vows of poverty, chastity, and obedience.
8. Brit.a nurse in charge of a hospital ward; head nurse.
9. a fellow black woman.
10. a woman who supports, promotes, or participates in feminism.
11. Informal.a form of address used to a woman or girl, esp. jocularly or contemptuously: Listen, sister, you've had enough.
—adj. 1. being or considered a sister; related by or as if by sisterhood: sister ships. 2. having a close relationship with another because of shared interests, problems, or the like: We correspond with school children in our sister city. 3. Biochem.being one of an identical pair.