1A female cousin — the daughter of one's aunt or uncle. Spoken Japanese uses the gender-neutral いとこ for any cousin; the distinction shows up only in writing, where a female cousin is 従姉妹 (従姉 if older, 従妹 if younger) and a male one is 従兄弟. Even spelled with these kanji the word is normally read いとこ; the on'yomi じゅうしまい is stiff, document-style Japanese found in family registers and legal texts.
従姉妹と久しぶりに会って、夜遅くまで話し込んだ。
I met up with my cousin after a long time, and we ended up talking late into the night.
姉の結婚式では、従姉妹が受付を手伝ってくれた。
At my older sister's wedding, my cousin helped out at the reception desk.
母方の従姉妹は、私より三つ年上だ。
My cousin on my mother's side is three years older than me.
幼い頃は、従姉妹とよく人形で遊んだものだ。
When I was little, I used to play with dolls with my cousin all the time.