exception

ɪkˈsɛpʃ(ə)n
ɛkˈsɛpʃ(ə)n

noun

a person or thing that is excluded from a general statement or does not follow a rule.

he always plays top tunes, and tonight was no exception

anomaly,irregularity,deviation,special case,departure,inconsistency,quirk,peculiarity,abnormality,oddity,outlier,edge case,misfit,freak