1. A problem or challenge that is not immediately obvious or easily perceived; an obstacle that requires careful attention to recognize
The project had a subtle difficulty that only became apparent after months of testing.
O projeto tinha uma dificuldade sutil que só se tornou aparente após meses de testes.
2. A nuanced or delicate complication in understanding, implementation, or resolution
There is a subtle difficulty in translating idioms between languages.
Há uma dificuldade sutil em traduzir expressões idiomáticas entre línguas.