a female offspring having both parents in common with another offspring; female sibling.

Also called half sister. a female offspring having only one parent in common with another offspring.

stepsister.

a female friend or protector regarded as a sister.

a thing regarded as feminine and associated as if by kinship with something else

The ships are sisters.

a female fellow member, as of a church.

a female member of a religious community that observes the simple vows of poverty, chastity, and obedience.

British . a nurse in charge of a hospital ward; head nurse.

a fellow black woman.

a woman who supports, promotes, or participates in feminism.

Informal . a form of address used to a woman or girl, esp. jocularly or contemptuously

Listen, sister, you've had enough.

being or considered a sister; related by or as if by sisterhood

sister ships.

having a close relationship with another because of shared interests, problems, or the like

We correspond with school children in our sister city.

Biochemistry . being one of an identical pair.

noun

blood sister , kin , kinsperson , relation , relative , twin , companion , female , friend , nun , sibling , woman