Definition of Leaf Object in Network Encyclopedia.
What is Leaf Object?
Leaf Object is an element in the directory hierarchy that is the endpoint of a branch and cannot contain other objects in the way that containers can. An example of a leaf object is a mailbox in the directory of Microsoft Exchange Server, which is found within the Recipients container.
You can view and manage objects in the Exchange directory hierarchy using the Exchange Administrator tool.

The term “leaf object” can also describe an endpoint of a branch in Active Directory of Microsoft Windows Server. Leaf objects (or terminal objects) are found in containers such as organizational units (OUs) and cannot contain other directory objects. You can view and manage objects in Active Directory using Microsoft Management Console (MMC) by installing snap-ins such as Active Directory Users and Computers and Active Directory Sites and Services.