Source : Webster's Revised Unabridged Dictionary (1913)

Apsidal \Ap"si*dal\, a.
   1. (Astron.) Of or pertaining to the apsides of an orbit.

   2. (Arch.) Of or pertaining to the apse of a church; as, the
      apsidal termination of the chancel.

Source : WordNet®

apsidal
     adj : of or relating an apse