younger female cousin
Specifically a female cousin who is younger than the speaker. Compare 従姉 (older female cousin), 従弟 (younger male cousin), and 従兄 (older male cousin).
See also: 従姉
My younger female cousin will graduate from high school next year.
My younger female cousin came to visit during summer vacation.
Standard kanji spelling for a younger female cousin. The reading いとこ is a jukujikun (special kanji reading).
The kanji 従 means 'follow' or 'obey', and 妹 means 'younger sister', together indicating a younger female relative. The reading いとこ is a jukujikun, a native Japanese word assigned to these kanji.