dry moat
A moat without water, typically part of Japanese castle defenses.
This castle is surrounded by a deep dry moat.
Standard kanji spelling for a dry moat.
Variant using 濠, a less common character for moat.
Compound of 空 (から, 'empty') and 堀 (ほり, 'moat, canal'), with rendaku voicing ほり → ぼり.