The Collaborative International Dictionary of English v.0.48:

Mohurrum \Mo*hur"rum\, Muharram \Mu*har"ram\, n. [Ar. muharram,
   prop., sacred, forbidden, n., the first month of the
   Mohammedan lunar year.]
   1. The first month of the Mohammedan year. --Whitworth.
      [1913 Webster]

   2. A festival of the Shiah sect of the Mohammedans held
      during the first ten days of the month Mohurrum.
      [1913 Webster]