What is "sage on the stage"

alt. (context education sometimes mildly derogatory English) An educator, especially at the postsecondary level, who imparts knowledge by lecture to an audience; the method of imparting knowledge used by such an educator. n. (context education sometimes mildly derogatory English) An educator, especially at the postsecondary level, who imparts knowledge by lecture to an audience; the method of imparting knowledge used by such an educator.