hull-down

Hull-down describes a ship or vehicle positioned so that only its upper portion is visible, with the hull hidden below the horizon or behind terrain.

The term originated in naval warfare, where a ship's masts and superstructure appear before its hull when approaching from a distance: The lookout spotted a vessel hull-down on the horizon.

In armored warfare, a tank goes hull-down when positioned behind a ridge with only its turret exposed, minimizing its target profile while maintaining the ability to fire.