Irregularity; a departure from the common rule.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
A turning from the natural order; anything that deviates from the common rule.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
Any departure from the type characteristics.
- A dictionary of scientific terms. By Henderson, I. F.; Henderson, W. D. Published 1920. (noun) (n.) (noun)
Irregularity: deviation from rule.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
Irregularity; deviation from rule; the angular distance of a planet from its perihelion; an irregularity in a planet's motion; slight deviation from a perfect interval.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)

Usage examples:

He is deeply impressed with the anomaly of his case, but has not the slightest objection to fasten the responsibility on somebody, never for a moment supposing the law would interpose against the exercise of his very best inclinations.
- Our World, or, The Slaveholders Daughter by F. Colburn Adams
The absence of the tower is an anomaly but is one method of solving the problem of the connexion between nave and chancel in the cruciform plan.
- The Ground Plan of the English Parish Church by A. Hamilton Thompson
Perhaps the most curious anomaly of experience is that of the child of the London slums who goes " hopping" into some of the loveliest parts of Kent, in early autumn.
- The Child Under Eight by E.R. Murray and Henrietta Brown Smith