A violation of rules.
An object or event that is not regular or ordinary.
An instance of being irregular.
Irregular bowel movement (e.g. diarrhea or constipation).
The state or condition of being irregular, or the extent to which something is irregular.
The highest order of derivative (the differentiability class) over a given domain.
The condition of being smooth; the degree or measure of said condition.
The quantity measured by the modulus of smoothness.