The Collaborative International Dictionary of English v.0.48:

Presumption \Pre*sump"tion\ (?; 215), n. [L. praesumptio: cf. F.
   pr['e]somption, OF. also presumpcion. See Presume.]
   1. The act of presuming, or believing upon probable evidence;
      the act of assuming or taking for granted; belief upon
      incomplete proof.
      [1913 Webster]

   2. Ground for presuming; evidence probable, but not
      conclusive; strong probability; reasonable supposition;
      as, the presumption is that an event has taken place.
      [1913 Webster]

   3. That which is presumed or assumed; that which is supposed
      or believed to be real or true, on evidence that is
      probable but not conclusive. "In contradiction to these
      very plausible presumptions." --De Quincey.
      [1913 Webster]

   4. The act of venturing beyond due beyond due bounds; an
      overstepping of the bounds of reverence, respect, or
      courtesy; forward, overconfident, or arrogant opinion or
      conduct; presumptuousness; arrogance; effrontery.
      [1913 Webster]

            Thy son I killed for his presumption. --Shak.
      [1913 Webster]

            I had the presumption to dedicate to you a very
            unfinished piece.                     --Dryden.
      [1913 Webster]

   Conclusive presumption. See under Conclusive.

   Presumption of fact (Law), an argument of a fact from a
      fact; an inference as to the existence of one fact not
      certainly known, from the existence of some other fact
      known or proved, founded on a previous experience of their
      connection; supposition of the truth or real existence of
      something, without direct or positive proof of the fact,
      but grounded on circumstantial or probable evidence which
      entitles it to belief. --Burrill. --Best. --Wharton.

   Presumption of law (Law), a postulate applied in advance to
      all cases of a particular class; e. g., the presumption of
      innocence and of regularity of records. Such a presumption
      is rebuttable or irrebuttable.
      [1913 Webster]

WordNet (r) 3.0 (2006):

presumption
    n 1: an assumption that is taken for granted [syn: given,
         presumption, precondition]
    2: (law) an inference of the truth of a fact from other facts
       proved or admitted or judicially noticed
    3: audacious (even arrogant) behavior that you have no right to;
       "he despised them for their presumptuousness" [syn:
       presumption, presumptuousness, effrontery,
       assumption]
    4: a kind of discourtesy in the form of an act of presuming;
       "his presumption was intolerable"

Moby Thesaurus II by Grady Ward, 1.0:

235 Moby Thesaurus words for "presumption":
   adventurousness, allegory, allusion, apriorism, aptitude,
   arcane meaning, arrogance, aspiration, assumption, assurance,
   assured faith, attitude, audaciousness, audacity, axiom, basis,
   belief, bias, boldness, brashness, brass, brazenness, brinkmanship,
   bumptiousness, butting-in, chance, cheek, cheekiness,
   cheerful expectation, chutzpah, climate of opinion, coloration,
   common belief, community sentiment, conceit, concept, conception,
   conclusion, confidence, conjecture, connotation, consensus gentium,
   consideration, contumely, conviction, courage fou,
   courting disaster, crust, daredevilry, daredeviltry, daring,
   deduction, dependence, desire, doomed hope, effrontery, entailment,
   estimate, estimation, ethos, evidence, expectation, eye, face,
   fair expectation, fair prospect, faith, familiarity,
   favorable prospect, feasibility, feeling, fervent hope,
   fire-eating, flirting with death, foolhardiness, forejudgment,
   forwardness, gall, general belief, going for broke, good chance,
   good cheer, good hope, great expectations, grounds, guess,
   guesswork, hardihood, harebrainedness, high hopes, hint, hope,
   hopeful prognosis, hopefulness, hopes, hoping, hoping against hope,
   hubris, hypothesis, idea, immodesty, impertinence, implication,
   implied meaning, import, imposition, impression, impudence,
   inference, innuendo, inquisitiveness, insolence, intermeddling,
   intimation, intrusiveness, involvement, ironic suggestion,
   judgment, lawlessness, liability, liberties, liberty abused,
   license, licentiousness, lights, likelihood, likeliness, meaning,
   meddlesomeness, meddling, metaphorical sense, mind, mystique,
   nerve, notion, nuance, observation, obtrusiveness, occult meaning,
   odds, officiousness, opinion, outlook, overconfidence, overtone,
   overweening, overweeningness, parti pris, personal judgment,
   plausibility, playing with fire, point of view, popular belief,
   posit, position, postulate, postulation, postulatum, posture,
   prayerful hope, preapprehension, preconception, preconclusion,
   preconsideration, predecision, predetermination, predilection,
   predisposition, prejudgment, prejudication, prejudice,
   premature judgment, premise, premiss, prenotion, prepossession,
   presumptive evidence, presumptuousness, presupposal,
   presupposition, presurmise, prevailing belief, pride, probabilism,
   probability, procacity, promise, proposition, prospect, prospects,
   public belief, public opinion, pushiness, reaction, reason,
   reasonable ground, reasonable hope, reliance, sanguine expectation,
   security, sentiment, set of postulates, sight, stance, stand,
   subsense, subsidiary sense, subsumption, suggestion, supposal,
   supposing, supposition, surmise, suspicion, symbolism, temerity,
   tendency, theory, thesis, thinking, thought, tinge, touch, trust,
   undercurrent, undermeaning, undertone, undue liberty, uppishness,
   uppityness, verisimilitude, view, way of thinking,
   well-grounded hope, working hypothesis



Bouvier's Law Dictionary, Revised 6th Ed (1856):

PRESUMPTION, evidence. An inference as to the existence of one fact, from
the existence of some other fact, founded on a previous experience of their
connexion. 3 Stark. Ev. 1234; 1 Phil. Ev. 116; Gilb. Ev. 142; Poth. Tr. des.
Ob. part. 4, c. 3, s. 2, n. 840. Or it, is an opinion, which circumstances,
give rise to, relative to a matter of fact, which they are supposed to
attend. Menthuel sur les Conventions, liv. 1, tit. 5.
     2. To constitute such a presumption, a previous experience of the
connexion between the known and inferred facts is essential, of such a
nature that as soon as the existence of the one is established, admitted or
assumed, an inference as to the existence of the other arises, independently
of any reasoning upon the subject. It follows that an inference may be
certain or not certain, but merely, probable, and therefore capable of being
rebutted by contrary proof.
     3. In general a presumption is more or less strong according as the
fact presumed is a necessary, usual or infrequent consequence of the fact or
facts seen, known, or proven. When the fact inferred is the necessary
consequence of the fact or facts known, the presumption amounts to a proof
when it is the usual, but not invariable consequence, the presumption is
weak; but when it is sometimes, although rarely,the consequence of the fact
or facts known, the presumption is of no weight. Menthuel sur les
Conventions, tit. 5. See Domat, liv. 9, tit. 6 Dig. de probationibus et
praesumptionibus.
     4. Presumptions are either legal and artificial, or natural.
     5.-1. Legal or artificial presumptions are such as derive from the law
a technical or artificial, operation and effect, beyond their mere natural.
tendency to produce belief, and operate uniformly, without applying the
process of reasoning on which they are founded, to the circumstances of the
particular case. For instance, at the expiration of twenty years, without
payment of interest on a bond, or other acknowledgment of its existence,
satisfaction is to be presumed; but if a single day less than twenty years
has elapsed, the presumption of satisfaction from mere lapse of time, does
not arise; this is evidently an artificial and arbitrary distinction. 4
Greenl. 270; 10 John. R. 338; 9 Cowen, R. 653; 2 McCord, R. 439; 4 Burr.
1963; Lofft, 320; 1 T. R. 271; 6 East, R. 215; 1 Campb. R. 29. An example of
another nature is given under this head by the civilians. If a mother and
her infant at the breast perish in the same conflagration, the law presumes
that the mother survived, and that the infant perished first, on account of
its weakness, and on this ground the succession belongs to the heirs of the
mother. See Death, 9 to 14.
     6. Legal presumptions are of two kinds: first, such as are made by the
law itself, or presumptions of mere law; secondly, such as are to be made by
a jury, or presumptions of law and fact.
     7.-1st. Presumptions of mere law, are either absolute and conclusive;
as, for instance, the presumption of law that a bond or other specialty was
executed upon a good consideration, cannot be rebutted by evidence, so long
as the instrument is not impeached for fraud; 4 Burr. 2225; or they are not
absolute, and may be rebutted evidence; for example, the law presumes that a
bill of exchange was accepted on a good consideration, but that presumption
may be rebutted by proof to the contrary.
     8.-2d. Presumptions of law and fact are such artificial presumptions as
are recognized and warranted by the law as the proper inferences to be made
by juries under particular circumstances; for instance, au unqualified
refusal to deliver up the goods on demand made by the owner, does not fall
within any definition of a conversion, but inasmuch as the detention is
attended with all the evils of a conversion to the owner, the law makes it,
in its effects and consequences, equivalent to a conversion, by directing or
advising the jury to infer a conversion from the facts of demand and
refusal.
     9.-2. Natural presumptions depend upon their own form and efficacy in
generating belief or conviction on the mind, as derived from these
connexions which are pointed out by experience; they are wholly independent
of any artificial connexions and relations, and differ from mere
presumptions of law in this essential respect, that those depend, or rather
are a branch of the particular system of jurisprudence to which they belong;
but mere natural presumptions are derived wholly by means of the common
experience of mankind, from the course of nature and the ordinary habits of
society.
     Vide, generally, Stark. Ev. h.t.; 1 Phil. Ev. 116; Civ. Code of Lo.
2263 to 2267; 17 Vin. Ab. 567; 12 Id. 124; 1 Supp. to Ves. jr. 37, 188, 489;
2 Id. 51, 223, 442; Bac. Ab. Evidence, H; Arch. Civ. Pl. 384; Toull. Dr.
Civ. Fr. liv. 3, t. 3, o. 4, s. 3; Poth. Tr. des Obl. part 4, c. 3, s. 2;
Matt. on Pres.; Gresl. Eq. Ev. pt. 3, c. 4, 363; 2 Poth. Ob. by Evans, 340;
3 Bouv. Inst. n. 3058, et seq.