A junk dimension is a dimension filled with minor data (text attributes, flags, indicators) that are marginally related, or even unrelated to one another. More importantly, each piece of datum in a junk dimension does not easily fit into other dimensions.
Junk dimensions are created to contain the “left over” pieces of data that emerge when dimensions are built. These data don’t fit naturally into any particular dimension (product, customer, vendor, etc.). Rather than create an entirely new dimension for just one or two pieces of datum, or deleting the datum altogether, these extraneous pieces of information will be placed in a junk dimension with other difficult to-categorize data.
http://www.1keydata.com/datawarehousing/junk-dimension.html http://en.wikipedia.org/wiki/Dimension_%28data_warehouse%29#Junk_dimension http://www.information-management.com/news/1027074-1.html