(adj) used of the younger of two persons of the same name especially used to distinguish a son from his father, Syn. jr., Example:John Junior; John Smith, Jr.
The Collaborative International Dictionary of English (GCIDE) v.0.53 Collaborative International Dictionary (GCIDE)
n. One who is younger; an inferior in age; a junior. “The elder shall serve the younger.” Rom. ix. 12. [ 1913 Webster ]
2. Used of the younger of two persons of the same name especially used to distinguish a son from his father; -- usually used postpositionally; as, Henry the younger. Syn. -- jr. [ WordNet 1.5 ]