Definition of “anomaly”

noun

1. something anomalous
2. deviation from the normal or usual order, type, etc; irregularity
3. astronomy 
   1. Also called true anomalythe angle between a planet, the sun, and the previous perihelion of the planet
   2. Also called eccentric anomalythe angle between the periapsis of a particular point on a circle round the orbit as seen from the centre of the orbit. This point is obtained by producing a perpendicular to the major axis of the ellipse through the orbiting body until it reaches the circumference of the circle
   3. Also called mean anomalythe angle between the periapsis of an orbit and the position of an imaginary body orbiting at a constant angular speed and in the same period as the real orbiting body
4. geology 
   1. Also called gravity anomalya deviation from the normal value of gravity at the earth's surface, caused by density differences at depth, for example those caused by a buried mineral body
   2. Also called magnetic anomalya magnetic field, for example one produced by a buried mineral body, that deviates from an expected or standard value, usually that of the earth's magnetic field