The Collaborative International Dictionary of English v.0.48:

Ideat \I*de"at\, Ideate \I*de"ate\, n. [LL. ideatum. See
   Idea.] (Metaph.)
   The actual existence supposed to correspond with an idea; the
   correlate in real existence to the idea as a thought or
   existence.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ideate \I*de"ate\, v. t.
   1. To form in idea; to fancy. [R.]
      [1913 Webster]

            The ideated man . . . as he stood in the intellect
            of God.                               --Sir T.
                                                  Browne.
      [1913 Webster]

   2. To apprehend in thought so as to fix and hold in the mind;
      to memorize. [R.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

ideate
    v 1: form a mental image of something that is not present or
         that is not the case; "Can you conceive of him as the
         president?" [syn: imagine, conceive of, ideate,
         envisage]