Pre*sump"tion (?; 215), n. [L. praesumptio: cf. F. présomption, 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.

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.