1 ferocious, savage, wild, truculent, brutish, feral, bestial, tigerish, brutal, cruel, fell, murderous, bloodthirsty, sanguinary, homicidal, barbaric, barbarous, inhuman, dangerous:
The fierce beasts will tear you limb from limb.
2 intractable, angry, furious, hostile, aggressive, vehement, frenzied, stormy, violent, turbulent, wild, tempestuous, tumultuous, raging, merciless, uncontrollable:
The old curmudgeon is in a fierce mood again today. A fierce storm raged for three days.
3 severe, awful, dreadful, intense, keen, dire, bitter, biting, racking:
Wear warm clothes to protect you from the fierce cold.