The Collaborative International Dictionary of English v.0.48:

Postulation \Pos`tu*la"tion\, n. [L. postulatio: cf. F.
   postulation.]
   The act of postulating, or that which is postulated;
   assumption; solicitation; suit; cause.
   [1913 Webster]

WordNet (r) 3.0 (2006):

postulation
    n 1: (logic) a declaration of something self-evident; something
         that can be assumed as the basis for argument [syn:
         postulation, predication]
    2: a formal message requesting something that is submitted to an
       authority [syn: request, petition, postulation]