The Collaborative International Dictionary of English v.0.48:

conceptualize \conceptualize\ v. t.
   1. to to form a concept of; as, He could not conceptualize a
      robot that would help paralyzed patients.

   Syn: conceive, conceive of, conceptualise, ideate.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

conceptualize
    v 1: have the idea for; "He conceived of a robot that would help
         paralyzed patients"; "This library was well conceived"
         [syn: gestate, conceive, conceptualize,
         conceptualise]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "conceptualize":
   appreciate, apprehend, be acquainted with, be apprised of,
   be aware of, be cognizant of, be conscious of, be conversant with,
   be informed, cerebrate, cogitate, cognize, coin, comprehend,
   conceit, conceive, concoct, create, discern, dream up,
   entertain ideas, exercise the mind, experience imaginatively,
   fabricate, fancy, fantasize, fathom, fictionalize, form ideas,
   grasp, hatch, have, have information about, have knowledge of,
   ideate, imagine, intellectualize, invent, ken, know, make out,
   mold, originate, perceive, possess, prehend, produce, realize,
   reason, recognize, savvy, see, seize, shape, suppose, think,
   think up, understand, wot, wot of