My understanding is that it simply means Churchyard, Antrim (since Antrim has already been mentioned). BTW, "Castle xxxx" is probably Castle Street in Antrim.
Just to note the following Church of Ireland baptisms, the address for all is Antrim (town), the parents are Alexander and Esther Loughlin, his occupation is mason in all bar one: Esther Loughlin 28 September 1828; Catherine Loughlin 25 December 1830; Anne Loughlin 28 April 1833 (father Alexander's occupation = nailer); Matilda Loughlin 16 August 1835; David Loughlin 17 May 1840; Thomas Loughlin 12 November 1843.