- without the faculty of reason; deprived of reason.
- without or deprived of normal mental clarity or sound judgment.
- not in accordance with reason; utterly illogical: irrational arguments.
- not endowed with the faculty of reason: irrational animals.
- (of a number) not capable of being expressed exactly as a ratio of two integers.
- (of a function) not capable of being expressed exactly as a ratio of two polynomials.
- Algebra. (of an equation) having an unknown under a radical sign or, alternately, with a fractional exponent.
- Greek and Latin Prosody.
- of or relating to a substitution in the normal metrical pattern, especially a long syllable for a short one.
- noting a foot or meter containing such a substitution.
- Mathematics. irrational number.
Origin of irrational
SynonymsSee more synonyms for irrational on Thesaurus.com
Examples from the Web for irrationally
According to her personal blog, “Irrationally Optimistic,” Zhang is a mother of two, living in a “double professional household.”Yahoo’s Accused Sexual Harasser Asked Women to Wear More Skirts at Work
July 14, 2014
The predominant school of thought holds that the markets are irrationally acting—and crashing—in response to the news.Let’s All Please Stop Overreacting to Bernanke’s Remarks
June 20, 2013
The latest incident will give new life to the gossip that Trierweiler is irrationally jealous of Royal.France’s Valerie Trierweiler Tweets Against Segolene Royal
June 12, 2012
It would be better to spend rationally now than irrationally in the heat of an election year.Larry Summers’ Impossible Stimulus Dream
June 14, 2011
It diminishes what they add to society, irrationally elevating their private lives in ways that do a disservice to them and to us.Who Cares What Tiger Did?
November 28, 2009
Irrationally, impulsively, unaccountably one loved one's country.Changing Winds
St. John G. Ervine
We were unweighted, irrationally agile with the slight gravity.
She felt trapped, and irrationally angry at him for recognizing her.Rebels of the Red Planet
Charles Louis Fontenay
He did not know why he was so irrationally happy, for nothing was changed in his life or hers.Ethan Frome
Merle, you must be very ill when you talk so irrationally and untruthfully.Professor Huskins
Lettie M. Cummings
- inconsistent with reason or logic; illogical; absurd
- incapable of reasoning
- not rational
- (as noun)an irrational
- prosody (in Greek or Latin verse)
- of or relating to a metrical irregularity, usually the occurrence of a long syllable instead of a short one
- denoting a metrical foot where such an irregularity occurs
Word Origin and History for irrationally
late 15c., "not endowed with reason" (of beats, etc.); earlier (of quantities) "inexpressible in ordinary numbers" (late 14c.); from Latin irrationalis "without reason," from assimilated form of in- "not, opposite of" (see in- (1)) + rationalis "reason" (see rational). Meaning "illogical, absurd" is attested from 1640s. Related: Irrationally.
- Not rational; marked by a lack of accord with reason or sound judgment.