cadetEnglishOxford New American Dictionarycadet /kəˈdet, kəˈdɛt / ▸ noun 1 a young trainee in the armed services or police force: an air force cadet. ▪ a student in training at a military school. 2 formal or archaic a younger son or daughter: a cadet of the family of the Earls of Rosse. ▪ [usually as modifier] a junior branch of a family: a cadet branch of the family. – DERIVATIVES cadetship /kəˈdetˌSHip, kəˈdɛtˌʃɪp / noun– ORIGIN early 17th century (in cadet (SENSE 2)): from French, from Gascon dialect capdet, a diminutive based on Latin caput ‘head’. The notion ‘little head’ or ‘inferior head’ gave rise to that of ‘younger, junior’.