Used to distinguish a son from his father when they have the same given name. Intended for or including youthful persons: a junior sports league. Lower in rank or shorter in length of tenure: a junior officer; the junior senator. Of, for, or constituting students in the third year of a U.S. high school or college: the junior class. Lesser in scale than the usual. A person who is younger than another: a sister four years my junior. A person lesser in rank or time of participation or service; subordinate. A student in the third year of a U.S. high school or college. A class of clothing sizes for girls and slender women. Also called junior miss.