This is the 16560th most frequent Russian word.
свирепый
Fierce; ferocious.
In this sentence, 'свирепый' describes the bear as frightening, wild, or aggressive, indicating a dangerous and menacing demeanor.
В лесу разгуливал свирепый медведь.
A ferocious bear roamed the forest.
Here, 'свирепую' metaphorically intensifies the determination, portraying it as intense and unwavering.
Он проявил свирепую решимость добиться своего.
He showed fierce determination to achieve his goal.
In this context, 'свирепо' modifies the verb 'spreads', meaning the rumor spread aggressively or uncontrollably.