Measuring roughly 6.5 metres long and 3.8 metres wide, the subrectangular hollow runs on a north-west to south-east axis, and along its eastern edge the stonework has not entirely disappeared: definite traces of stone-facing remain visible, suggesting a constructed void rather than a natural dip in the earth.

The feature is believed to mark the site of a souterrain, an underground passage or chamber built during the early medieval period, typically by cutting into the earth and lining the walls and roof with stone. Souterrains were commonly associated with ringforts and cashels, the latter being stone-walled enclosures that served as farmsteads or defended settlements. Their exact purposes are still debated, but they are generally thought to have been used for storage, refuge, or both. The cashel at Cahermorris is a separate recorded monument in its own right, and this depression sits within its north-western quadrant as a secondary feature, a possible remnant of whatever internal arrangements once made the enclosure functional as a living or working space.