A clan, tribe, or family, proceeding from a common progenitor; -- used especially of the ancient clans in Ireland.

an Irish variant of "clan", used to denote a branch of a clan known by a different surname than that of the clan chief or progenitor (the clan name)

A branch of a clan or a family who sought protection of a clan

A family not having the name of the clan, but associated with the clan and entitled to wear its tartan, e.g. Kirkland is a sept of Clan Maxwell and Clan Douglas.