Source : Webster's Revised Unabridged Dictionary (1913)

Holocaust \Hol"o*caust\, n. [L. holocaustum, Gr. ?, neut. of ?,
   ?, burnt whole; "o'los whole + kaysto`s burnt, fr. kai`ein to
   burn (cf. {Caustic}): cf. F. holocauste.]
   1. A burnt sacrifice; an offering, the whole of which was
      consumed by fire, among the Jews and some pagan nations.
      --Milton.

   2. Sacrifice or loss of many lives, as by the burning of a
      theater or a ship.

   Note: [An extended use not authorized by careful writers.]

Source : WordNet®

holocaust
     n 1: an act of great destruction and loss of life
     2: the Nazi program of exterminating Jews under Hitler [syn: {final
        solution}]