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
2. Ground for presuming; evidence probable, but not
conclusive; strong probability; reasonable supposition;
as, the presumption is that an event has taken place.
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.
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.
Thy son I killed for his presumption. --Shak.
I had the presumption to dedicate to you a very
unfinished piece. --Dryden.
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.