WordNet (r) 3.0 (2006):

Belshazzar
    n 1: (Old Testament) Babylonian general and son of
         Nebuchadnezzar II; according to the Old Testament he was
         warned of his doom by divine handwriting on the wall that
         was interpreted by Daniel (6th century BC)

Easton's 1897 Bible Dictionary:

Belshazzar
   Bel protect the king!, the last of the kings of Babylon (Dan.
   5:1). He was the son of Nabonidus by Nitocris, who was the
   daughter of Nebuchadnezzar and the widow of Nergal-sharezer.
   When still young he made a great feast to a thousand of his
   lords, and when heated with wine sent for the sacred vessels his
   "father" (Dan. 5:2), or grandfather, Nebuchadnezzar had carried
   away from the temple in Jerusalem, and he and his princes drank
   out of them. In the midst of their mad revelry a hand was seen
   by the king tracing on the wall the announcement of God's
   judgment, which that night fell upon him. At the instance of the
   queen (i.e., his mother) Daniel was brought in, and he
   interpreted the writing. That night the kingdom of the Chaldeans
   came to an end, and the king was slain (Dan. 5:30). (See
   NERGAL-SHAREZER.)

     The absence of the name of Belshazzar on the monuments was
   long regarded as an argument against the genuineness of the Book
   of Daniel. In 1854 Sir Henry Rawlinson found an inscription of
   Nabonidus which referred to his eldest son. Quite recently,
   however, the side of a ravine undermined by heavy rains fell at
   Hillah, a suburb of Babylon. A number of huge, coarse
   earthenware vases were laid bare. These were filled with
   tablets, the receipts and contracts of a firm of Babylonian
   bankers, which showed that Belshazzar had a household, with
   secretaries and stewards. One was dated in the third year of the
   king Marduk-sar-uzur. As Marduk-sar-uzar was another name for
   Baal, this Marduk-sar-uzur was found to be the Belshazzar of
   Scripture. In one of these contract tablets, dated in the July
   after the defeat of the army of Nabonidus, we find him paying
   tithes for his sister to the temple of the sun-god at Sippara.


Hitchcock's Bible Names Dictionary (late 1800's):

Belshazzar, master of the treasure