[Term] Delegate [Definition] 
A rich client that is authorized to impersonate another client. For example, consider a situation in which a user-facing website, Web1, calls an infrastructure data service, Data2. It might be advantageous for Web1 to impersonate its users when it accesses Data2. Web1 contacts a federation server to obtain claims that represent one of its users. When it is contacted, the federation server can determine whether Web1 is an authorized delegate and, if so, it can allow the impersonation. If it is authorized, Web1 accesses Data2 while acting as the user.