horizontal moat; horizontal trench
A moat or trench dug horizontally, often in the context of Japanese castle fortifications. Contrasts with 竪堀 (たてぼり), a vertical trench.
See also: 竪堀
A horizontal moat was dug around the castle.
They strengthened the defenses by combining horizontal and vertical trenches.
Compound of 横 (よこ, 'horizontal') and 堀 (ほり, 'moat, trench'), with rendaku voicing ほり → ぼり.