What is the medieval term for a defensive ditch that is not filled with water?

The story behind the answer

Medieval fortification manuals and castle archaeology use this term for a purpose-built moat left unfilled with water. It creates a deep obstacle with steep scarp and counterscarp that breaks charges, stalls siege towers and ladders, and exposes attackers to missiles; builders might line it with masonry, add stakes or palisades, and cut it V-shaped to be harder to cross.

Such features were common on hilltop sites or in porous soils where flooding was impractical, and they were cheaper to maintain yet often as effective as wet moats. By contrast, a sunken way is a protected road along a defense line, dry ditch is a generic description rather than the standard term in castle studies, and earthwork moat is not a recognized medieval classification.