Adjective

(en adjective)

Nonstandard; not conforming to rules or expectations.

* {{quote-book

, year = 1967 , first = Barbara , last = Sleigh , authorlink = Barbara Sleigh , title = (Jessamy) , edition = 1993 , location = Sevenoaks, Kent , publisher=Bloomsbury , isbn = 0 340 19547 9 , page = 33 , url = , passage = ‘ “It would be most irregular' Grandpa!” says Miss Cecily frowning and tapping her foot. “Well, we’re a pretty ' irregular family so that’s neither here nor there,” says the old man, impish like. [...] ’ }}

Of a surface, rough.

Without symmetry, regularity, or uniformity.

*{{quote-book, year=1944, author=(w)

, title= The Three Corpse Trick, chapter=5 , passage=The hovel stood in the centre of what had once been a vegetable garden, but was now a patch of rank weeds. Surrounding this, almost like a zareba, was an irregular ring of gorse and brambles, an unclaimed vestige of the original common.}}

* {{quote-magazine, date=2013-01-01, author=Paul Bartel, Ashli Moore

, volume=101, issue=1, page=47–48, magazine=(American Scientist) , title= Avian Migration: The Ultimate Red-Eye Flight , passage=Many of these classic methods are still used, with some modern improvements. For example, with the aid of special microphones and automated sound detection software, ornithologists recently reported […] that pine siskins (Spinus pinus ) undergo an irregular , nomadic type of nocturnal migration.}}

* {{quote-magazine, date=2013-07-19, author= Ian Sample

, volume=189, issue=6, page=34, magazine=(The Guardian Weekly) , title= Irregular bedtimes may affect children's brains , passage=Irregular bedtimes may disrupt healthy brain development in young children, according to a study of intelligence and sleeping habits.  ¶ Going to bed at a different time each night affected girls more than boys, but both fared worse on mental tasks than children who had a set bedtime, researchers found.}}

Not regular; having sides that are not equal or angles that are not equal.

Whose faces are not all regular polygons (or are not equally inclined to each other).

Adjective

(en adjective)

Not rational; unfounded or nonsensical.

an irrational decision

* July 18 2012 , Scott Tobias, AV Club The Dark Knight Rises [http://www.avclub.com/articles/the-dark-knight-rises-review-batman,82624/]

Where the Joker preys on our fears of random, irrational acts of terror, Bane has an all-consuming, dictatorial agenda that’s more stable and permanent, a New World Order that’s been planned out with the precision of a military coup.

(mathematics, arithmetic, number theory, not comparable) Of a real number, that cannot be written as the ratio of two integers.

The number π is irrational .