1. by means of unofficial, irregular, or unethical procedures; not following proper protocol or established procedures
The documents were obtained through improper channels, which raised serious questions about their validity.
Os documentos foram obtidos por canais impróprios, o que levantou sérias questões sobre sua validade.
2. using illegitimate or corrupt methods to accomplish something
He tried to get the contract through improper channels instead of going through the official bidding process.
Ele tentou obter o contrato por canais impróprios em vez de passar pelo processo de licitação oficial.