Definitions
1.nounA student at a military school who is training to be an officer.
2.nounA younger or youngest son, who would not inherit as a firstborn son would.
3.noun(in compounds, chiefly in genealogy) Junior. (See also the heraldic term cadency.)"a cadet branch of the family"
4.nounA young man who makes a business of ruining girls to put them in brothels.
5.nounA young gentleman learning sheep farming at a station; also, any young man attached to a sheep station.