1. A reddish-brown oxide of iron that forms on the surface of iron or steel when exposed to oxygen and moisture
The old gate was covered in rust.
O portão antigo estava coberto de ferrugem.
2. In botany, a fungal disease that affects plants, characterized by reddish or brownish pustules
The wheat crop suffered from rust this season.
A plantação de trigo sofreu com ferrugem nesta estação.
3. Figuratively, a state of deterioration or decline due to lack of use or neglect
His skills had gathered rust over the years.
Suas habilidades juntaram ferrugem ao longo dos anos.