1. the quality of being fierce; intense aggression, violence, or hostility
2. extreme intensity or strength of feeling, action, or natural force

Examples

• The lion’s fierceness made all the other animals flee.
• She fought with such fierceness that her opponents were intimidated.
• The fierceness of the storm knocked down power lines throughout the city.
• His fierceness in defending his beliefs impressed everyone at the debate.
• The fierceness of her determination helped her overcome every obstacle.
• The wind’s fierceness made it impossible to keep the tent upright.