Wal Marde is a french, specifically from Quebec in Canada, parody of Wal Mart found commonly on t-shirts. Marde is French, and means shit in English, although it spelled incorrectly. Merde is the correct spelling, but as a result of Wal Mart being involved, the t-shirts say Wal Marde.
Wal-Mart?! I think its Wal-Marde!