noun
younger male second cousin
Specifically a male second cousin who is younger than the speaker. The term is precise but not commonly used in everyday conversation; many speakers simply say はとこ or describe the relationship more generally.
彼は私の再従弟で、まだ大学生です。
He is my younger second cousin and still a university student.
Compound of 再 (sai, 'again' or 'second') and 従弟 (jūtei, 'younger male cousin'), literally 'second younger male cousin'.