Source : Webster's Revised Unabridged Dictionary (1913)

Claustral \Claus"tral\, a. [F., fr. LL. claustralis, fr. L.
   claustrum. See {Cloister}.]
   Cloistral. --Ayliffe

Claustrum \Claus"trum\, n.; pl. {Claustra}. [L., a bolt or bar.]
   (Anat.)
   A thin lamina of gray matter in each cerebral hemisphere of
   the brain of man. -- {Claus"tral}, a.