osso duro de roer
Portuguese
Etymology
Literally, “hard bone to gnaw”.
Noun
osso duro de roer m (plural ossos duros de roer, metaphonic)
- (idiomatic) hard nut to crack (problem that is challenging to solve)
- (idiomatic) hard nut to crack (situation, person, group, etc. which is difficult to overcome or deal with)
- (idiomatic) a brave or hardy person or organisation