Source : Webster's Revised Unabridged Dictionary (1913)

Dura mater \Du"ra ma"ter\ [L., lit., hard mother. The membrane
   was called mater, or mother, because it was formerly thought
   to give rise to every membrane of the body.] (Anat.)
   The tough, fibrous membrane, which lines the cavity of the
   skull and spinal column, and surrounds the brain and spinal
   cord; -- frequently abbreviated to dura.

Source : WordNet®

dura mater
     n : the outermost (and toughest) of the 3 meninges [syn: {dura}]