Map Obfuscation is a method in which you make it hard for people who open your map to understand what everything is and does. Generally, this is in an attempt to make your map more Closed Source, rather than Open Source (See Open Source and Closed Source. Note: Don't obfuscate your version of the map that you edit, or you'll end up being really confused. Alternatively, write in a text file what each changed name means, and refer to that.
Manual obfuscation is basically manually making variable names, object names, unit names, etc. hard to understand, either by typing random letters (dgfgsdgergsdgd) for each name, or unexplanatory names (v1, v2, v3, v4 etc.). While it may take some time, this method is quite solid.
Rodrigo, the maker of Nexus Word War and Debates, has been using quite a clever method to protect its SC2Bank files: he mixes lower-case 'L', capital 'i', and possibly the character '|' (to verify), to protect his banks.
For example, try to determine the difference between: llIIlIlll and IlIIllllI. It is pretty hard, indeed. Of course, you could start copy-pasting every single code in a text-editor program and change their font, but you are kind of forced to admit it could discourage quite a few people.
You can use programs to automatically obfuscate your map data. Currently only one exists: StragusMapster's Data Obfuscation Tool.