Noun

1. An isolated context, with its own virtual address space, in which an application runs, analogous to a process in an operating system.
   • 2002, Michael Stiefel, Robert J Oberg, Application development using C# and .NET‎

     Next we create a new thread, and that thread creates a new application domain, loads, and executes an assembly.

   • 2004, Simon Robinson, Christian Nagel, Karli Watson, Jay Glynn, Morgan Skinner, Bill Evjen, Professional C#‎

     .NET Remoting can be used for accessing objects in another application domain.

   • 2006, Stefan Schackow, Professional ASP.NET 2.0 security, membership, and role management‎

     All managed code in the .NET Framework needs to run within an application domain.