The Collaborative International Dictionary of English v.0.48:

Scholium \Scho"li*um\, n.; pl. L. Scholia, E. Scholiums.
   [NL., fr. Gr. ?, fr. ?. See School.]
   1. A marginal annotation; an explanatory remark or comment;
      specifically, an explanatory comment on the text of a
      classic author by an early grammarian.
      [1913 Webster]

   2. A remark or observation subjoined to a demonstration or a
      train of reasoning.
      [1913 Webster]

WordNet (r) 3.0 (2006):

scholium
    n 1: a marginal note written by a scholiast (a commentator on
         ancient or classical literature) [syn: scholium,
         scholia]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "scholium":
   adversaria, aide-memoire, annotation, apparatus criticus, comment,
   commentary, commentation, docket, entry, exegesis, footnote, gloss,
   item, jotting, marginal note, marginalia, memo, memoir, memorandum,
   memorial, minutes, notation, note, note of explanation, register,
   registry, reminder, scholia, word of explanation