Definition of "Junior" :
noun: the younger of two persons
"She is two years my junior."
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
"Look here, junior, it's none of your business."
adjective: used of the third or next to final year in United States high school or college
"The junior class."
adjective: including or intended for youthful persons
"A junior sports league."
adjective: younger; lower in rank; shorter in length of tenure or service