An MSD file is a map file created by the mapping software ArcGIS Desktop.
These files can be used in conjunction with ArcGIS Server, where they can be uploaded and hosted for viewing at a later date or by another user or computer.
.msd File
Extension
Developer:
ESRI
File category:
What are msd files & how to open them - Map Service Definition File
File category:
Developer:
ESRI