What survives is an arc roughly twenty-five metres long, a bank of earth standing about one and a quarter metres high, now built into a stone field wall. The rest of the enclosure it once belonged to appears to have been levelled entirely, leaving this single sweep of bank as the only visible evidence that something more complete once stood here.

The site is tentatively identified as the remains of an enclosure, the kind of roughly circular or oval earthwork, typically defined by a bank and internal ditch, that appears widely across Ireland and is associated broadly with early medieval settlement and farming. Enclosures of this type were often the boundary of a farmstead or small settlement, enclosing a living area or protecting livestock. At Killacoosane, the surviving arc sits on a gentle south-west facing slope, a practical orientation that would have offered shelter and winter light to whoever once made use of the ground within. The incorporation of the old bank into a later stone field boundary is a common fate for such earthworks; farmers working the same land across successive centuries found it easier to reuse an existing rise in the ground than to remove it, and so the earlier feature was absorbed rather than erased, at least in part.