The Collaborative International Dictionary of English v.0.48:

Ennead \En"ne*ad\, n. [Gr. ?, ?, fr. 'enne`a nine.]
   The number nine or a group of nine.
   [1913 Webster]

   The Enneads, the title given to the works of the
      philosopher Plotinus, published by his pupil Porphyry; --
      so called because each of the six books into which it is
      divided contains nine chapters.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ennead
    n 1: the cardinal number that is the sum of eight and one [syn:
         nine, 9, IX, niner, Nina from Carolina, ennead]