An Olog-hai is humanoid. It can regenerate itself. It is a carnivore.
But at the end of the Third Age a troll-race not before seen appeared in southern Mirkwood and in the mountain borders of Mordor. Olog-hai they were called in the Black Speech. That Sauron bred them none doubted, though from what stock was not known. Some held that they were not Trolls but giant Orcs; but the Olog-hai were in fashion of body and mind quite unlike even the largest of Orc-kind, whom they far surpassed in size and power. Trolls they were, but filled with the evil will of their master: a fell race, strong, agile, fierce and cunning, but harder than stone. Unlike the older race of the Twilight they could endure the Sun... They spoke little, and the only tongue they knew was the Black Speech of Barad-dur. The Return of the King, by J.R.R. Tolkien