outwork

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]

outwork
n : subsidiary defensive structure lying outside the main
fortified area; "the outworks of the castle"