1. A choice or judgment made that has negative consequences or is considered unwise
Leaving school was a bad decision that he later regretted.
Deixar a escola foi uma má decisão que ele se arrependeu depois.
2. An action taken that proves to be harmful, foolish, or counterproductive
Investing all his money in that company was a bad decision.
Investir todo seu dinheiro naquela empresa foi uma má decisão.