Being beyond or out of the common order or rule; not of the usual, customary, or regular kind; not ordinary: as, extraordinary evils require extraordinary remedies.Not pertaining to a regular system or sequence; exceptional; special: as, an extraordinary courier or messenger; an ambassador extraordinary; the extraordinary jurisdiction of a court; a gazette extraordinary.In universities, relating to studies outside of the regular curriculum, or to lectures not recognized by the university as of the first rank of importance.Exceeding the common degree or measure; hence, remarkable; uncommon; rare; wonderful: as, the extraordinary genius of Shakspere; an edifice of extraordinary grandeur.Synonyms Unusual, singular, extra, unwonted, signal, egregious, marvelous, prodigious, strange, preposterous.n. Anything uncommon or unusual; a thing exceeding the usual order, practice, or method.n. An express messenger or courier.n. Extra expense or indulgence.n. In the British service, an allowance to troops beyond the gross pay, such as the expenses for barracks, encampments, etc.Remarkably; exceptionally; extraordinarily.