This is a bullaun stone, a type of ancient carved or worn basin stone found across Ireland, typically in association with early ecclesiastical sites. The basin here is roughly 26 to 28 centimetres across and about 16 centimetres deep, positioned slightly off-centre on a boulder measuring just over a metre in length. The water that tends to collect in these hollows was long regarded as having curative or protective properties, and the stones themselves are thought to date in many cases to the early medieval period, though their precise origins and functions remain debated among archaeologists.

What makes Ballinacorbeg particularly notable is that this is not an isolated example. The ecclesiastical enclosure here contains three bullaun stones in total, which is an unusual concentration for a single site. The boulder in question sits approximately 15 metres north of the north-east corner of the wall surrounding the church and graveyard, placing it just beyond the formal boundary of the sacred enclosure while remaining clearly associated with it. The clustering of multiple bullaun stones at one location sometimes suggests a site of sustained ritual or devotional significance across a long span of time, though the specific history of this enclosure is not fully documented.