noun
Familiar, affectionate term for one's niece. Used in casual family contexts.
See also: 姪
姪っ子が遊びに来た。
My niece came over to visit.
姪っ子の誕生日プレゼントを買った。
I bought a birthday present for my niece.
Derived from 姪 (めい, 'niece') with the diminutive suffix っ子 (っこ), adding a familiar, affectionate tone.