The Collaborative International Dictionary of English v.0.48:

Mausoleum \Mau`so*le"um\, n.; pl. E. Mausoleums, L. -lea.
   [L. mausoleum, Gr. ?, fr. ? Mausolus, king of Caria, to whom
   Artemisia, his widow, erected a stately monument, one of the
   wonders of the ancient world.]
   A magnificent tomb, or stately sepulchral monument.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mausoleum
    n 1: a large burial chamber, usually above ground

The Devil's Dictionary (1881-1906):

MAUSOLEUM, n.  The final and funniest folly of the rich.