Definition of "Oldcastle"

A town in County Meath, Ireland.  examples

A former civil parish in Cheshire West and Chester borough, Cheshire, England, abolished in 2015; the hamlet of Oldcastle Heath is in this area (OS grid ref SJ4745).  examples

An area and ward in Bridgend county borough, Wales (OS grid ref SS9079).  examples

A small village in Crucorney community, Monmouthshire, Wales, near the border with England (OS grid ref ST3224).  examples

An unincorporated community in Tecumseh, Ontario, Canada.  examples