ferocious

adjective

1 bears are ferocious animals:

fierce, savage, wild, feral, untamed;

predatory, rapacious, ravening, aggressive, dangerous.

▷antonyms tame; gentle.

2 a ferocious attack on an innocent man:

brutal, brutish, vicious, violent, bloody, barbarous, barbaric, savage, sadistic, ruthless, remorseless, cruel, pitiless, merciless, heartless, bloodthirsty, murderous, tigerish, wolfish;

wicked, inhuman, monstrous, abominable, fiendish, hellish, diabolical;

British, informal beastly;

literary fell;

archaic sanguinary.

▷antonyms gentle.

3 the ferocious midday sun | a ferocious headache:

intense, extreme, strong, powerful, fierce, burning, searing;

severe, acute, unbearable, insufferable, hellish, diabolical.

▷antonyms mild.

ferocious Oxford Dictionary of English