Source : Webster's Revised Unabridged Dictionary (1913)

Ogdoad \Og"do*ad\, n. [Gr. ?, ?, from ? eight.]
   A thing made up of eight parts. --Milman.

Source : WordNet®

ogdoad
     n : the cardinal number that is the sum of seven and one [syn: {eight},
          {8}, {VIII}, {eighter}, {eighter from Decatur}, {octad},
          {octonary}, {octet}]