The Collaborative International Dictionary of English v.0.48:

Ideation \I`de*a"tion\, n.
   The faculty or capacity of the mind for forming ideas; the
   exercise of this capacity; the act of the mind by which
   objects of sense are apprehended and retained as objects of
   thought.
   [1913 Webster]

         The whole mass of residua which have been accumulated .
         . . all enter now into the process of ideation. --J. D.
                                                  Morell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ideation
    n 1: the process of forming and relating ideas

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "ideation":
   IQ, abstract thought, act of thought, apprehension, brainwork,
   caliber, capacity, cerebration, clairvoyance, cogitation, command,
   comprehension, conceit, conception, conceptualization,
   creative thought, deductive power, esemplastic power, excogitation,
   foreknowledge, grasp, grip, headwork, heavy thinking, idea,
   imageless thought, integrative power, intellect, intellection,
   intellectual exercise, intellectual grasp, intellectual power,
   intellectualism, intellectuality, intellectualization,
   intelligence, intelligence quotient, knowledge, mastery,
   mental act, mental age, mental capacity, mental grasp,
   mental labor, mental process, mental ratio, mentality, mentation,
   mother wit, native wit, noesis, power of mind, precognition,
   prehension, ratiocination, rationality, reasoning, reasoning power,
   sanity, savvy, scope of mind, sense, straight thinking, thinking,
   thinking aloud, thinking out, thinking power, thought,
   understanding, wisdom, wit