1. A difficult, demanding, or laborious project, task, or job that requires significant effort, perseverance, and dedication to complete
Completing the research project was an arduous undertaking that took months of hard work.
Completar o projeto de pesquisa foi uma empreitada árdua que levou meses de trabalho intenso.
2. An ambitious or challenging assignment that presents obstacles and demands considerable commitment
Building the new highway was an arduous undertaking for the construction company.
Construir a nova rodovia foi uma empreitada árdua para a empresa de construção.