meninx

from WordNet (r) 3.0 (2006)

meninx
    n 1: a membrane (one of 3) that envelops the brain and spinal
         cord [syn: {meninx}, {meninges}]

from The Collaborative International Dictionary of English v.0.48

Meninges \Me*nin"ges\ (m[-e]*n[i^]n"j[=e]z), n. pl.; sing.
   {Meninx} (m[-e]*n[i^][ng]ks"). [NL., fr. Gr. mh^nigx,
   mh^niggos, a membrane.] (Anat.)
   The three membranes that envelop the brain and spinal cord;
   the pia mater, dura mater, and arachnoid membrane.
   [1913 Webster]