a. 1. (Astron.) Of or pertaining to the apsides of an orbit. [ 1913 Webster ]
2. (Arch.) Of or pertaining to the apse of a church; as, the apsidal termination of the chancel. [ 1913 Webster ]
a. [ L. apex, apicis, tip or summit. ] At or belonging to an apex, tip, or summit. Gray. [ 1913 Webster ]