Source : Webster's Revised Unabridged Dictionary (1913)

Scholiast \Scho"li*ast\, n. [Gr. ?, fr. ? a scholium: cf. F.
   scoliate. See {Scholium}.]
   A maker of scholia; a commentator or annotator.

         No . . . quotations from Talmudists and scholiasts . .
         . ever marred the effect of his grave temperate
         discourses.                              --Macaulay.

Source : WordNet®

scholiast
     n : a scholar who writes explanatory notes on an author
         (especially an ancient commentator on a classical author)