This is the 6991st most frequent Polish word.
groźny
Dangerous; threatening.
In this context, 'groźny' describes the dog as being threatening or capable of causing harm.
Ten pies jest bardzo groźny.
This dog is very dangerous.
Here, 'groźny' is used to characterize the hurricane as a natural phenomenon that poses a threat.
Groźny huragan zbliża się do wybrzeża.
A dangerous hurricane is approaching the coastline.
In this case, 'groźny' refers to the tone of the person's voice as intimidating or filled with menace.