WordNet (r) 3.0 (2006):

Japheth
    n 1: (Old Testament) son of Noah

Easton's 1897 Bible Dictionary:

Japheth
   wide spreading: "God shall enlarge Japheth" (Heb. Yaphat Elohim
   le-Yephet, Gen. 9:27. Some, however, derive the name from
   _yaphah_, "to be beautiful;" hence white), one of the sons of
   Noah, mentioned last in order (Gen. 5:32; 6:10; 7:13), perhaps
   first by birth (10:21; comp. 9:24). He and his wife were two of
   the eight saved in the ark (1 Pet. 3:20). He was the progenitor
   of many tribes inhabiting the east of Europe and the north of
   Asia (Gen. 10:2-5). An act of filial piety (9:20-27) was the
   occasion of Noah's prophecy of the extension of his posterity.

     After the Flood the earth was re-peopled by the descendants of
   Noah, "the sons of Japheth" (Gen. 10:2), "the sons of Ham" (6),
   and "the sons of Shem" (22). It is important to notice that
   modern ethnological science, reasoning from a careful analysis
   of facts, has arrived at the conclusion that there is a
   three-fold division of the human family, corresponding in a
   remarkable way with the great ethnological chapter of the book
   of Genesis (10). The three great races thus distinguished are
   called the Semitic, Aryan, and Turanian (Allophylian). "Setting
   aside the cases where the ethnic names employed are of doubtful
   application, it cannot reasonably be questioned that the author
   [of Gen. 10] has in his account of the sons of Japheth classed
   together the Cymry or Celts (Gomer), the Medes (Madai), and the
   Ionians or Greeks (Javan), thereby anticipating what has become
   known in modern times as the 'Indo-European Theory,' or the
   essential unity of the Aryan (Asiatic) race with the principal
   races of Europe, indicated by the Celts and the Ionians. Nor can
   it be doubted that he has thrown together under the one head of
   'children of Shem' the Assyrians (Asshur), the Syrians (Aram),
   the Hebrews (Eber), and the Joktanian Arabs (Joktan), four of
   the principal races which modern ethnology recognizes under the
   heading of 'Semitic.' Again, under the heading of 'sons of Ham,'
   the author has arranged 'Cush', i.e., the Ethiopians; 'Mizraim,'
   the people of Egypt; 'Sheba and Dedan,' or certain of the
   Southern Arabs; and 'Nimrod,' or the ancient people of Babylon,
   four races between which the latest linguistic researches have
   established a close affinity" (Rawlinson's Hist. Illustrations).