A mumak is, in The Lord of the Rings, an enormous elephant, slow but ferocious. While not the most dangerous of the quadrupeds, the mumakil can do large amounts of damage, and can withstand significant blows before succumbing. In fact, they have the most powerful single melee attack in the game other than the Riders', making a mockery of all but the thickest armor. Mumakil have a thick body, so they take no damage from kicks among other things. While stronger characters like valkyries or barbarians should be sufficiently prepared for the encounter, mumakil tend to be a frequent reason of death for weaker characters trying to fight them in melee.
When fighting a mumak, take advantage of its slowness - use ranged weapons, polearms, wands, spells, or hit and run. The plural of mumak is mumakil.