violently hostile or aggressive; combative or pugnacious
lacking restraint or control; violent or heated
a fierce argument
extremely intense or severe
fierce pain
furiously active or determined
Let's make a fierce effort to finish this project on time
said of a mechanism: operating with a sharp and powerful action
These brakes are a bit fierce
fiercely adv
fierceness noun
[Middle English fiers via Old French from Latin ferus wild, savage]