1. A challenging journey or mission undertaken to explore, discover, or accomplish a specific objective, characterized by significant obstacles, hardships, or uncertainties
The Arctic expedition proved to be a difficult expedition due to extreme weather conditions.
A expedição do Ártico provou ser uma expedição difícil devido às condições climáticas extremas.
2. A complex or arduous undertaking requiring considerable effort, resources, and perseverance to achieve its goals
Organizing the mountain climbing expedition was a difficult expedition that took months of planning.
Organizar a expedição de montanhismo foi uma expedição difícil que levou meses de planejamento.