The Ursva was the name of a fictional Klingon freighter assumed in communications by the crew of the USS Enterprise-A during their incursion into the Klingon Empire to rescue James T. Kirk and Leonard McCoy from imprisonment on Rura Penthe.
Although the crew's Klingonese was less than perfect, it was passable enough to gain them entry into Klingon space, when they were contacted by a listening post on Morska. (Star Trek VI: The Undiscovered Country)