Source : Webster's Revised Unabridged Dictionary (1913)

Anomaly \A*nom"a*ly\, n.; pl. {Anomalies}. [L. anomalia, Gr. ?.
   See {Anomalous}.]
   1. Deviation from the common rule; an irregularity; anything
      anomalous.

            We are enabled to unite into a consistent whole the
            various anomalies and contending principles that are
            found in the minds and affairs of men. --Burke.

            As Professor Owen has remarked, there is no greater
            anomaly in nature than a bird that can not fly.
                                                  --Darwin.

   2. (Astron.)
      (a) The angular distance of a planet from its perihelion,
          as seen from the sun. This is the true anomaly. The
          eccentric anomaly is a corresponding angle at the
          center of the elliptic orbit of the planet. The mean
          anomaly is what the anomaly would be if the planet's
          angular motion were uniform.
      (b) The angle measuring apparent irregularities in the
          motion of a planet.

   3. (Nat. Hist.) Any deviation from the essential
      characteristics of a specific type.

Source : WordNet®

anomaly
     n 1: deviation from the normal or common order or form or rule
          [syn: {anomalousness}]
     2: a person who is unusual [syn: {unusual person}]
     3: (astronomy) position of a planet as defined by its angular
        distance from its perihelion (as observed from the sun)