The Collaborative International Dictionary of English v.0.48:

Assumption \As*sump"tion\ (?; 215), n. [OE. assumpcioun a taking
   up into heaven, L. assumptio a taking, fr. assumere: cf. F.
   assomption. See Assume.]
   1. The act of assuming, or taking to or upon one's self; the
      act of taking up or adopting.
      [1913 Webster]

            The assumption of authority.          --Whewell.
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   2. The act of taking for granted, or supposing a thing
      without proof; supposition; unwarrantable claim.
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            This gives no sanction to the unwarrantable
            assumption that the soul sleeps from the period of
            death to the resurrection of the body. --Thodey.
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            That calm assumption of the virtues.  --W. Black.
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   3. The thing supposed; a postulate, or proposition assumed; a
      supposition.
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            Hold! says the Stoic; your assumption's wrong.
                                                  --Dryden.
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   4. (Logic) The minor or second proposition in a categorical
      syllogism.
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   5. The taking of a person up into heaven. Hence: (Rom. Cath.
      & Greek Churches) A festival in honor of the ascent of the
      Virgin Mary into heaven.
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U.S. Gazetteer (1990):

Assumption, IL (city, FIPS 2609)
  Location: 39.51796 N, 89.04843 W
  Population (1990): 1244 (579 housing units)
  Area: 2.3 sq km (land), 0.0 sq km (water)
  Zip code(s): 62510

Moby Thesaurus II by Grady Ward, 1.0:

281 Moby Thesaurus words for "assumption":
   a priori principle, about-face, acceptance, accession, acquisition,
   admission, admittance, adoption, affirmation, alchemy, allegory,
   allusion, anointing, anointment, apotheosis, appointment,
   appropriation, apriorism, arcane meaning, arrogation, ascension,
   ascent, aspiration, assertion, assignment, assimilation,
   assumed position, assumption, assurance, assured faith, attitude,
   authorization, axiom, basis, beatification, becoming,
   borrowed plumes, canonization, categorical proposition, change,
   change-over, cheerful expectation, climate of opinion,
   colonization, coloration, common belief, community sentiment,
   conceit, concept, conception, conclusion, confidence, conjecture,
   connotation, conquest, consecration, consensus gentium,
   consideration, conversion, conviction, copying, coronation, data,
   deification, delegation, dependence, deputation, derivation,
   deriving, desire, doomed hope, election, elevation, empowerment,
   encroachment, enshrinement, enslavement, entailment, erection,
   escalation, estimate, estimation, ethos, exaltation, expectation,
   eye, fair prospect, faith, familiarity, feeling, fervent hope,
   first principles, flip-flop, foundation, fundamental, gathering,
   general belief, getting, good cheer, good hope, great expectations,
   ground, growth, guess, guesswork, height, high hopes, hint, hope,
   hopeful prognosis, hopefulness, hopes, hoping, hoping against hope,
   hubris, hypothesis, hypothesis ad hoc, idea, imitation,
   implication, implied meaning, import, imposition, impression,
   indent, inference, infringement, innuendo, insolence, intimation,
   invasion, involvement, ironic suggestion, judgment, lapse, law,
   lawlessness, legitimate succession, lemma, liberties,
   liberty abused, license, licentiousness, lifting, lights,
   major premise, meaning, metaphorical sense, mind, minor premise,
   mocking, mystique, naturalization, notion, nuance, observation,
   occult meaning, occupation, opinion, overtone, overweening,
   overweeningness, passage, pasticcio, pastiche, personal judgment,
   philosopheme, philosophical proposition, pirating, plagiarism,
   plagiary, playing God, point of view, popular belief, posit,
   position, postulate, postulation, postulatum, posture,
   prayerful hope, preemption, premise, preoccupation, prepossession,
   presumption, presumptuousness, presupposal, presupposition,
   prevailing belief, principle, progress, promise, proposition,
   propositional function, prospect, prospects, public belief,
   public opinion, raising, re-formation, reaction, rearing, receipt,
   receival, receiving, reception, reconversion, reduction, reliance,
   requisition, resolution, resurrection, reversal,
   sanguine expectation, security, seizure, sentiment,
   set of postulates, shift, sight, simulation, stance, statement,
   subjugation, subsense, subsidiary sense, subsumption, succession,
   suggestion, sumption, supposal, supposing, supposition, surmise,
   sursum corda, switch, switch-over, symbolism, takeover, taking,
   taking over, the Ascension, the Assumption, theorem, theory,
   thesis, thinking, thought, tinge, touch, transformation, transit,
   transition, translation, trespass, trespassing, trust, truth table,
   truth-function, truth-value, turning into, undercurrent,
   undermeaning, undertone, undue liberty, upbuoying, upcast,
   upheaval, uplift, uplifting, upping, uprearing, upthrow, upthrust,
   usurpation, view, volte-face, way of thinking, well-grounded hope,
   working hypothesis