甥おいっ子こおいっこMeanings1nounnephewfamiliar languageFamiliar, affectionate term for one's nephew, used in casual conversation.甥おいっ子こが遊あそびに来きた。My nephew came over to play.甥おいっ子この誕たん生じょう日びプレゼントを買かった。I bought a birthday present for my nephew.