From WordNet (r) 2.0 (August 2003) [wn]:
junior
adj 1: younger; lower in rank; shorter in length of tenure or
service [ant: senior]
2: used of the third or next to final year in United States
high school or college; "the junior class"; "a third-year
student" [syn: {junior(a)}, third-year, next-to-last]
3: including or intended for youthful persons; "a junior sports
league"; "junior fashions"
n 1: term of address for a disrespectful and annoying male; "look
here, junior, it's none of your business"
2: a third-year undergraduate
3: the younger of two men
4: a son who has the same first name as his father [syn:
Junior, Jr, Jnr]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Junior \Jun"ior\, n.
1. A younger person.
[1913 Webster]
His junior she, by thirty years. --Byron.
[1913 Webster]
2. Hence: One of a lower or later standing; specifically, in
American colleges and four-year high schools, one in the
third year of his course, one in the fourth or final year
being designated a senior; in some seminaries, one in
the first year, in others, one in the second year, of a
three years' course.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Junior \Jun"ior\ (j[=u]n"y[~e]r; 277), a. [L. contr. fr.
juvenior, compar. of juvenis young. See Juvenile.]
[1913 Webster]
1. Less advanced in age than another; younger. Abbreviated
Jr.
[1913 Webster +PJC]
Note: Junior is applied to distinguish the younger of two
persons bearing the same name in the same family, and
is opposed to senior or elder. Commonly applied to a
son who has the same Christian name as his father.
[1913 Webster]
2. Lower in standing or in rank, or having entered later into
a position or office; as, a junior partner; junior
counsel; junior captain; the junior Senator from New York.
[1913 Webster]
3. Composed of juniors, whether younger or a lower standing;
as, the junior class; the junior baseball league; of or
pertaining to juniors or to a junior class. See Junior,
n., 2.
[1913 Webster]
4. Belonging to a younger person, or an earlier time of life.
[1913 Webster]
Our first studies and junior endeavors. --Sir T.
Browne.
[1913 Webster]
5. of or relating to the third year of a four-year term; --
used of the third or next to final year in a U. S. high
school or college. See junior[2], n..
Syn: third-year.
[WordNet 1.5 +PJC]