irregular
adjective
uk/ɪˈreɡjələr/ usnot happening at regular times or in regular amounts:
Many firms have an irregular cashflow.
You will not be penalised for contributing irregular amounts, or missing or stopping payments.
Airport staff inspect the runways three times a day at irregular intervals.
not according to usual rules or what is expected, and often not acceptable:
Investigators found these bank deposits to be highly irregular because the amount exceeded the man's income.
Certain irregular business practices were identified.