1. A subject, case, or issue that has been examined in great detail and with careful attention to all aspects
The police department assured the public that the crime was a thoroughly investigated matter.
O departamento de polícia garantiu ao público que o crime era um assunto minuciosamente investigado.
2. A topic that has undergone comprehensive examination leaving no significant questions unanswered
After years of research, this historical event is now a thoroughly investigated matter.
Após anos de pesquisa, este evento histórico é agora um assunto minuciosamente investigado.