Term defining a large truck or group of people that obstructs the flow of traffic, either intentionally or unintenionally. Taken from Starcraft, where Ultralisks commonly block up base entrances by accident, preventing zergling
s from entering or leaving.
Doug: Dammit, this semi is being a real ultralisk.
Steve: Well, I think you'll get a shot at passing it in a second, oh wait, he moved to keep you from passing. What an ultralisk.