The Uruk-hai, o, is a form of orc found in NetHack. They are very similar to Mordor orcs, but carry and use some or all of orcish cloaks, orcish short swords, iron shoes, orcish bows (with poisoned orcish arrows), and Uruk-hai shields (with a 2/3 chance of starting with each, in addition to a 50% chance of an orcish helm) instead of the Mordor orc's equipment. The poisoned arrows can very quickly end the game of those not used to facing Uruk-hai.
Unless you are poison resistant, you should try to avoid Uruk-hai whenever possible as their poisoned arrows may instantly kill you. In case you have to fight them, you should try to stay in melee range as they will prefer melee to ranged attacks.
As Uruk-hai are not poison resistant and appear in large groups, they may kill each other with their arrows trying to attack you. This can be helpful when fighting them in corridors.