The rath at Brenormore is a ringfort, a type of enclosed farmstead once ubiquitous across early medieval Ireland, typically dating from roughly the fifth to the twelfth centuries. Thousands survive in various states of preservation, but this one combines modest earthwork remains with a possible souterrain, an underground stone-lined passage or chamber that was commonly used for storage or as a place of refuge, which sets it slightly apart from the more straightforward examples.

The monument takes the form of a roughly circular enclosure some 27 metres in diameter. An earthen bank defines most of its circuit, standing about 0.75 metres above the interior and 1.5 metres above the exterior ground level, with a width of nearly 4 metres at its best-preserved stretches. On the eastern and southern sides the bank has been reduced to a simple scarp, still about 1.55 metres high. There appear to be two possible entrance gaps, one on the northern side roughly 3 metres wide and another on the western side at about 4 metres. A shallow fosse, the external ditch that would originally have reinforced the bank as a defensive or enclosing feature, survives as a faint trace on the south-western to western arc, no more than 0.3 metres deep. The interior slopes gently downhill toward the east, following the natural gradient of the hillside. Rabbit burrows have been noted in the bank, a reminder of how quietly damaging burrowing animals can be to earthwork archaeology over time.

A 10-metre forestry buffer zone runs around the monument and serves as a driving line for forestry operations, which means the rath sits at the edge of working land rather than in undisturbed isolation. The associated souterrain, recorded separately, adds a layer of complexity to what might otherwise appear a straightforward agricultural enclosure.