Definitions of junior:

• noun:   the younger of two men
• noun:   a third-year undergraduate
• noun:   a son who has the same first name as his father
• noun:   term of address for a disrespectful and annoying male

  Example: "Look here, junior, it's none of your business"

• adjective:   including or intended for youthful persons

  Example: "A junior sports league"

• adjective:   younger; lower in rank; shorter in length of tenure or service
• name:  A male given name (rare: 1 in 6250 males; popularity rank in the U.S.: #532)
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #12396)