The Collaborative International Dictionary of English v.0.48:

Varuna \Va*ru"na\ (v[.a]*r[udd]"n[.a]), n. [Skr. Varu[.n]a.]
   (Hindu Myth.)
   The god of the waters; the Indian Neptune. He is regarded as
   regent of the west, and lord of punishment, and is
   represented as riding on a sea monster, holding in his hand a
   snaky cord or noose with which to bind offenders, under
   water.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Varuna
    n 1: in Vedism, god of the night sky who with his thousand eyes
         watches over human conduct and judges good and evil and
         punishes evildoers; often considered king of the Hindu gods
         and frequently paired with Mitra as an upholder of the
         world