The Collaborative International Dictionary of English v.0.48:

Belial \Be"li*al\, n. [Heb. beli ya'al; beli without + ya'al
   profit.]
   An evil spirit; a wicked and unprincipled person; the
   personification of evil.
   [1913 Webster]

         What concord hath Christ with Belia ?    --2 Cor. vi.
                                                  15.
   [1913 Webster]

   A son (or man) of Belial, a worthless, wicked, or
      thoroughly depraved person. --1 Sam. ii. 12.
      [1913 Webster]

Easton's 1897 Bible Dictionary:

Belial
   worthlessness, frequently used in the Old Testament as a proper
   name. It is first used in Deut. 13:13. In the New Testament it
   is found only in 2 Cor. 6:15, where it is used as a name of
   Satan, the personification of all that is evil. It is translated
   "wicked" in Deut. 15:9; Ps. 41:8 (R.V. marg.); 101:3; Prov.
   6:12, etc. The expression "son" or "man of Belial" means simply
   a worthless, lawless person (Judg. 19:22; 20:13; 1 Sam. 1:16;
   2:12).


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

Belial, wicked, worthless