outwork n 1: subsidiary defensive structure lying outside the main fortified area; "the outworks of the castle"
Outwork \Out*work"\, v. t. To exceed in working; to work more or faster than. [1913 Webster]
Outwork \Out"work`\, n. (Fort.) A minor defense constructed beyond the main body of a work, as a ravelin, lunette, hornwork, etc. --Wilhelm. [1913 Webster]