A Ktorr Skann was a term used by the Vulcan civilization. Being declared a ktorr skann meant that the Vulcan in question was without a family as they had been banished from the household with them being forbidden of ever returning home due to the decisions they had made. Such decisions were not easy and were the formal cutting of ties between family members.
Sybok due to his practices which involved a rejection of Surak's teachings was also declared ktorr skann; an outcast who was considered dead by his family with his very existence being expunged from all records on Vulcan. (TOS novel: Star Trek V: The Final Frontier)