Merriam-Webster Collegiate Dictionary - irregular

 I. adjective  Etymology: Middle English irreguler, from Anglo-French, from Late Latin ~is not in accordance with rule, from Latin in- + regularis regular  Date: 14th century  1.  a. not being or acting in accord with laws, rules, or established custom ~ conduct  b. not conforming to the usual pattern of inflection ~ verbs; specifically strong 16  c. not following a usual or prescribed procedure; especially British celebrated without either proclamation of the banns or publication of intention to marry ~ marriage  2. not belonging to or a part of a regular organized group; specifically not belonging to a regular army but raised for a special purpose ~ troops  3.  a. lacking perfect symmetry or evenness an ~ coastline  b. having one or more floral parts of the same whorl different in size, shape, or arrangement; specifically zygomorphic  4. lacking continuity or regularity especially of occurrence or activity ~ employment  • ~ly adverb Synonyms:  ~, anomalous, unnatural mean not conforming to rule, law, or custom. ~ implies not conforming to a law or regulation imposed for the sake of uniformity in method, practice, or conduct concerned about his ~ behavior. anomalous implies not conforming to what might be expected because of the class or type to which it belongs or the laws that govern its existence her drive made her an anomalous figure in a sleepy organization. unnatural suggests what is contrary to nature or to principles or standards felt to be essential to the well-being of civilized society prisoners treated with unnatural cruelty.  II. noun  Date: 15th century one that is ~: as  a. a soldier who is not a member of a regular military force  b. plural merchandise that has minor defects or that falls next below the manufacturer's standard for firsts