Deviation from the normal or common order or form or rule WordNet 3.0 & Open English WordNet

In quantum physics an anomaly or quantum anomaly is the failure of a symmetry of a theory's classical action to be a symmetry of any regularization of the full quantum theory. Wikipedia

In the natural sciences, especially in atmospheric and Earth sciences involving applied statistics, an anomaly is a persisting deviation in a physical quantity from its expected value, e.g., the systematic difference between a measurement and a trend or a model prediction. Wikipedia

A failure of a symmetry of a theory's classical action Wikipedia Disambiguation

The failure of a symmetry of a theory's classical action to be a symmetry of any regularization of the full quantum theory Wikidata

A deviation from the common rule, type, or form. OmegaWiki

A failure of a classical symmetry due to quantum corrections. Wiktionary