General computing term.
Wikipedia: "Managed code is computer program code that requires and will execute only under the management of a Common Language Runtime virtual machine, typically the .NET Framework, or Mono. The term was coined by Microsoft.
Managed code is the compiler output of source code written in one of over twenty high-level programming languages that are available for use with the Microsoft .NET Framework, including C#, J#, Microsoft Visual Basic .NET, Microsoft JScript and .NET...
Managed code in the Microsoft .Net Framework is defined according to the Common Intermediate Language specification.
See also: unmanaged code.