Definition - What does Mono Silverlight mean?
Mono is an open-source implementation of the .NET Framework based on the ECMA standards using Common Language Runtime (CLR) and C#.
Techopedia explains Mono Silverlight
Silverlight is Microsoft’s answer to Adobe’s Flash for creating rich Internet applications. However, it is only available for Windows and Mac, not for Linux. This significantly reduces its market share and audience. To bring Silverlight 1.0 and 2.0 to UNIX and LINUX users, Microsoft made an agreement for collaboration with Novell in bringing the open-source implementation of Silverlight to the UNIX system. This will be done through the Mono development platform.
Novell has made an agreement with Microsoft to bring Silverlight 1.0 and 2.0 into Mono for it to be compatible with platforms or than Windows and Mac. Essentially Mono Silverlight is the open-source version of Microsoft’s Silverlight.