adj. (fiercer, fiercest) 1 vehemently aggressive or frightening in temper or action, violent. 2 eager, intense, ardent. 3 unpleasantly strong or intense; uncontrolled (fierce heat). 4 (of a mechanism) not smooth or easy in action. fiercely adv. fierceness n.
[ ME f. AF fers, OF fiers fier proud f. L ferus savage ]