The Collaborative International Dictionary of English v.0.48:

Preconceive \Pre`con*ceive"\, v. t. [imp. & p. p.
   Preconceived; p. pr. & vb. n. Preconceiving.]
   To conceive, or form an opinion of, beforehand; to form a
   previous notion or idea of.
   [1913 Webster]

         In a dead plain the way seemeth the longer, because the
         eye hath preconceived it shorter than the truth.
                                                  --Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

preconceived
    adj 1: (of an idea or opinion) formed beforehand; especially
           without evidence or through prejudice; "certain
           preconceived notions"

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "preconceived":
   anticipatory, beforehand, biased, forejudged, judged beforehand,
   preconceptual, preconcluded, predecided, predetermined,
   predisposed, predispositional, prejudged, prejudging, prejudiced,
   prejudicial, presumed, presupposed, presurmised