1. The greatest or most important work produced by an artist, writer, or other creative person; a masterpiece
Dante's Divine Comedy is considered his magnum opus.
A Divina Comédia de Dante é considerada sua obra-prima.
2. A person's most significant achievement or accomplishment
The architectural firm's magnum opus was the design of the new museum.
A obra-prima da empresa de arquitetura foi o projeto do novo museu.