stepsister

noun

Etymology: Etymology tree Proto-Indo-European *(s)tew- Proto-Germanic *steupa- Proto-West Germanic *steupa- Old English stēop- Middle English step- English step- Proto-Indo-European *swé Proto-Indo-European *h₁ésh₂r̥ Proto-Indo-European *su-h₁ésh₂-ōr? Proto-Indo-European *swé Proto-Indo-European *-sōr ? Proto-Indo-European *swésōrder. Proto-Germanic *swestēr Proto-West Germanic *swester Old English sweostor Middle English suster English sister English stepsister From step- + sister.

1. The daughter of one's stepparent by a previous relationship.
2. The stepdaughter of one's parent which is not one's half-sister.