1. A sign, signal, or indication that warns of danger or alerts someone to pay attention
The sudden drop in sales was a warning sign of economic trouble.
A queda repentina nas vendas foi um sinal de alerta de problemas econômicos.
2. A visible or audible signal used to alert people to a potential threat or emergency
The fire alarm served as an important warning sign during the building evacuation.
O alarme de incêndio serviu como um importante sinal de alerta durante a evacuação do edifício.
3. An indication or symptom that something negative may happen
Excessive fatigue can be a warning sign of serious illness.
O cansaço excessivo pode ser um sinal de alerta de doença grave.