1. An operation, activity, or business transaction that does not comply with legal regulations, proper procedures, or established rules
The customs authorities discovered an irregular operation at the port.
As autoridades aduaneiras descobriram uma operação irregular no porto.
2. In aviation, an operation that deviates from normal procedures or safety standards
The flight was canceled due to irregular operations in the airport.
O voo foi cancelado devido a operações irregulares no aeroporto.
3. An unlawful or clandestine business activity
The police raided several locations suspected of irregular operations.
A polícia fez buscas em vários locais suspeitos de operações irregulares.