The Collaborative International Dictionary of English v.0.48:

Conception \Con*cep"tion\, n. [F. conception, L. conceptio, fr.
   concipere to conceive. See Conceive.]
   1. The act of conceiving in the womb; the initiation of an
      embryonic animal life.
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            I will greaty multiply thy sorrow and thy
            conception.                           --Gen. iii.
                                                  16.
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   2. The state of being conceived; beginning.
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            Joy had the like conception in our eyes. --Shak.
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   3. The power or faculty of apprehending of forming an idea in
      the mind; the power of recalling a past sensation or
      perception.
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            Under the article of conception, I shall confine
            myself to that faculty whose province it is to
            enable us to form a notion of our past sensations,
            or of the objects of sense that we have formerly
            perceived.                            --Stewart.
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   4. The formation in the mind of an image, idea, or notion,
      apprehension.
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            Conception consists in a conscious act of the
            understanding, bringing any given object or
            impression into the same class with any number of
            other objects or impression, by means of some
            character or characters common to them all.
                                                  --Coleridge.
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   5. The image, idea, or notion of any action or thing which is
      formed in the mind; a concept; a notion; a universal; the
      product of a rational belief or judgment. See Concept.
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            He [Herodotus] says that the sun draws or attracts
            the water; a metaphorical term obviously intended to
            denote some more general and abstract conception
            than that of the visible operation which the word
            primarily signifies.                  --Whewell.
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   6. Idea; purpose; design.
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            Note this dangerous conception.       --Shak.
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   7. Conceit; affected sentiment or thought. [Obs.]
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            He . . . is full of conceptions, points of epigram,
            and witticism.                        --Dryden.

   Syn: Idea; notion; perception; apprehemsion; comprehension.
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WordNet (r) 3.0 (2006):

conception
    n 1: an abstract or general idea inferred or derived from
         specific instances [syn: concept, conception,
         construct] [ant: misconception]
    2: the act of becoming pregnant; fertilization of an ovum by a
       spermatozoon
    3: the event that occurred at the beginning of something; "from
       its creation the plan was doomed to failure" [syn:
       creation, conception]
    4: the creation of something in the mind [syn: invention,
       innovation, excogitation, conception, design]

Moby Thesaurus II by Grady Ward, 1.0:

287 Moby Thesaurus words for "conception":
   Calliope, Clio, Erato, Euterpe, IQ, Melpomene, Polyhymnia,
   Terpsichore, Thalia, Vernunft, Vorstellung, abstract thought,
   act of thought, appreciation, apprehension, approach, arrangement,
   artistic imagination, assumption, attack, attitude, authorship,
   beginning, birth, blueprint, blueprinting, brain, brains,
   brainwork, calculation, caliber, capacity, cerebration, charting,
   clairvoyance, climate of opinion, clue, cogitation, coinage,
   coming with child, command, commencement, common belief,
   community sentiment, comprehension, conceit, conceiving, concept,
   conceptualization, conclusion, concoction, consensus gentium,
   consideration, contrivance, contriving, creation, creative effort,
   creative imagination, creative power, creative thought,
   deductive power, derivation, design, device, devising,
   discourse of reason, discursive reason, disposition, eidetic image,
   emergence, enterprise, envisagement, envisaging, envisioning,
   esemplastic imagination, esemplastic power, esprit, estimate,
   estimation, ethos, excogitation, eye, fabrication, fancy, feeling,
   figuring, foreknowledge, foresight, forethought, formation,
   formulation, game, general belief, generation, genesis, genius,
   graphing, grasp, grass roots, gray matter, grip, ground plan,
   guidelines, hatching, head, headpiece, headwork, heavy thinking,
   idea, ideation, image, imageless thought, imagery, imagery study,
   imaging, imagism, imagistic poetry, imago, impression,
   improvisation, inauguration, inception, initiation, inkling,
   inspiration, integrative power, intellect, intellection,
   intellectual exercise, intellectual faculty, intellectual grasp,
   intellectual object, intellectual power, intellectualism,
   intellectuality, intellectualization, intelligence,
   intelligence quotient, intention, introduction, invention,
   judgment, knowledge, launch, launching, layout, lifelike image,
   lights, lineup, long-range plan, making do, mapping, master plan,
   mastery, memory-trace, mens, mental act, mental age,
   mental capacity, mental grasp, mental image, mental impression,
   mental labor, mental picture, mental process, mental ratio,
   mental representation, mentality, mentation, method, methodology,
   mind, mintage, mother wit, muse, mystique, mythicization,
   mythification, mythopoeia, native wit, noesis, notion, nous,
   objectification, observation, operations research, opinion,
   organization, origin, original, origination, outline, perception,
   personal judgment, picture, picturing, plan, planning,
   planning function, poetic imagery, poetic imagination,
   point of view, popular belief, position, posture, power of mind,
   power of reason, prearrangement, precognition, prehension,
   presumption, prevailing belief, procedure, program,
   program of action, proposal, provenience, psyche, public belief,
   public opinion, radical, radix, ratio, ratiocination, rationality,
   rationalization, reaction, reason, reasoning, reasoning faculty,
   reasoning power, recept, reflection, representation, rise, root,
   sanity, savvy, schedule, schema, schematism, schematization,
   scheme, scheme of arrangement, scope of mind, sense, sentiment,
   setup, shaping imagination, sight, smarts, source, stance, start,
   stem, stock, straight thinking, strategic plan, strategy,
   superfetation, superimpregnation, supposition, system,
   systematization, tactical plan, tactics, taproot, the big picture,
   the picture, theory, thinking, thinking aloud, thinking out,
   thinking power, thought, understanding, view, vision, visionary,
   visual image, visualization, way, way of thinking, wisdom, wit,
   word-painting, working plan