1. a daughter of one’s stepparent by a previous marriage

Examples

• My stepsister moved in with us when my dad remarried.
• She gets along well with her new stepsister.
• The two stepsisters share a bedroom in their blended family.
• Her stepsister is three years older than she is.
• They became close friends even though they’re only stepsisters.
• The wedding brought together two families, including his stepsister from California.