Any event or measurement that is out of the ordinary regardless of whether it is exceptional or not.
Any of various angular distances.
A defect or malformation.
A failure of a classical symmetry due to quantum corrections.
Something or someone that is strange or unusual.
A deviation from a rule or from what is regarded as normal; an outlier.
A problem or situation that occurs only at an extreme (maximum or minimum) operating parameter or under other unusual operating conditions.
Any unexpected input or user behaviour.