boyau
nounUK /ˈbwɑːjəʊ/
Etymology Borrowed from French boyau. Doublet of bowel.
1
Government, Military, Politics, War A small trench or ditch, typically built in a zigzag pattern, serving to connect or provide communication between two trenches, particularly the rear and front lines.
2
A line, drawn winding about, in order to enclose several tracts of land, or to attack some works.