1. A topic, theme, or matter that is identical to one previously mentioned or under discussion
We've already discussed that issue; let's not rehash the same subject again.
Já discutimos esse assunto; vamos não ficar mastigando o mesmo assunto novamente.
2. An identical or equivalent topic in different contexts or conversations
The teacher covered the same subject in both morning and afternoon classes.
O professor cobriu o mesmo assunto nas aulas da manhã e da tarde.