Hypertext Webster Gateway: "boyau"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Boyau \Boy"au\, n.; pl. {Boyaux} or {Boyaus}. [F. boyau gut, a
long and narrow place, and (of trenches) a branch. See
{Bowel}.] (Fort.)
A winding or zigzag trench forming a path or communication
from one siegework to another, to a magazine, etc.
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