CDF is a person with very high grade at school/university. It stands for Cú De Ferro, or literally iron ass. Probably due to the fact of staying many hours seated studying.
The old expression for CDF is “caxias”, and is still used by older people or in some places in Brazil.
- O Fabrício é o mais inteligente da sala!
- Eu sei, ele sempre foi o maior CDF.