A bullaun is a large stone, usually a boulder or slab, with one or more circular depressions ground into its surface. The hollows were almost certainly made by human hands, though exactly when, by whom, and for what purpose remains a matter of genuine debate among archaeologists. Theories range from the practical, grain-grinding or pigment preparation, to the ritual, with many bullauns accumulating folk associations around cursing, healing, and the power of rainwater collected in the bowl. The name itself derives from the Irish word for a bowl or hollow, and that simple description is often all the certainty available.

Bullaun stones are found throughout Ireland and are frequently associated with early medieval ecclesiastical sites, though they predate Christianity in many cases and were simply absorbed into later religious landscapes. Their distribution across Connacht is well documented, and Mayo has a reasonable share of them. The townland name Cloongullaun may itself encode something of this history; place names in the west of Ireland often preserve traces of long-vanished features, structures, or associations that the ground has otherwise swallowed. Beyond the classification and location of this particular stone, the available record is thin, which is not unusual for a category of monument that was rarely written about until relatively recently and that can be easy to overlook in a landscape full of competing antiquities.