A "Module Out of the Main Discipline".
A module being a specific topic you study, like you would a whole subject at A-Levels say.
These would not usually be part of your degree, but they replace some, allowing you to broaden the subject material you study.
Thursday 26th - MOMD Fair 10:30am-3:30pm, in the Great Hall
You could be studying BSc Economics, but decide to take a module as unrelated as "Introduction to Magnetic and Electronic Materials" for example, which is run by the Metallurgy and Materials department.
You need to complete 120 credits in each year (12 modules, 6 per semester usually). 20 of these credits can be an MOMD, for courses that allow you one, as not all of them do.
Your department will be able to confirm if you are able to take an MOMD, but as an idea it is usually the more vocational courses which don't allow it, as there isn't the leeway to study something not as related.
Some modules usually on offer range from modules amongst courses such as Social Studies, Engineering, Geography, Philosophy, Languages, Psychology, Mathematics etc. If your department doesn't allow MOMDs, you could still do a language course, through open access courses.
To find out the modules that are available, go to the MOMD Fair on the Thursday 26th September of Welcome Week. You can read up on the ones offered for the previous 12/13 academic year here.
"In most cases, you will be able to register for your preferred MOMD; however, some modules have limited spaces. Where this is the case, students will be allocated at random to fill the number of places available."