transitive trust

Transitive trust is a two-way relationship automatically created between parent and child domains in a Microsoft Active Directory forest. When a new domain is created, it shares resources with its parent domain by default, enabling an authenticated user to access resources in both the child and parent. 

In mathematics, the transitive property of equality states that if a = b and b = c, then a = c.  In an Active Directory transitive trust relationship, if domain A trusts domain B, and domain B trusts domain C, then domain A trusts domain C.