The Collaborative International Dictionary of English v.0.48:

Apodeictic \Ap"o*deic"tic\, Apodictic \Ap`o*dic"tic\,
Apodeictical \Ap`o*deic"tic*al\, Apodictical \Ap`o*dic"tic*al\,
   a. [L. apodicticus, Gr. ?, fr. ? to point out, to show by
   argument; ? from + ? to show.]
   Self-evident; intuitively true; evident beyond contradiction.
   --Brougham. Sir Wm. Hamilton.
   [1913 Webster] Apodeictically

WordNet (r) 3.0 (2006):

apodeictic
    adj 1: of a proposition; necessarily true or logically certain
           [syn: apodictic, apodeictic]