1something that deviates from what is standard, normal, or expected:there are a number of anomalies in the present system [with clause]:the apparent anomaly that those who produced the wealth were the poorest [mass noun]:the position abounds in anomaly
2 Astronomy the angular distance of a planet or satellite from its last perihelion or perigee.
late 16th century: via Latin from Greek anōmalia, from anōmalos(see anomalous)
anomaly in other Oxford dictionaries
Definition of anomaly in the US English dictionary