The Collaborative International Dictionary of English v.0.48:

Academic \Ac`a*dem"ic\, Academical \Ac`a*dem"ic*al\, a. [L.
   academicus: cf. F. acad['e]migue. See Academy.]
   1. Belonging to the school or philosophy of Plato; as, the
      Academic sect or philosophy.
      [1913 Webster]

   2. Belonging to an academy or other higher institution of
      learning; scholarly; literary or classical, in distinction
      from scientific. "Academic courses." --Warburton.
      "Academical study." --Berkeley.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Academic \Ac`a*dem"ic\, n.
   1. One holding the philosophy of Socrates and Plato; a
      Platonist. --Hume.
      [1913 Webster]

   2. A member of an academy, college, or university; an
      academician.
      [1913 Webster]

WordNet (r) 3.0 (2006):

academic
    adj 1: associated with academia or an academy; "the academic
           curriculum"; "academic gowns"
    2: hypothetical or theoretical and not expected to produce an
       immediate or practical result; "an academic discussion"; "an
       academic question"
    3: marked by a narrow focus on or display of learning especially
       its trivial aspects [syn: academic, donnish, pedantic]
    n 1: an educator who works at a college or university [syn:
         academician, academic, faculty member]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "academic":
   abstract, armchair, book-learned, bookish, booky, chimerical,
   classroom, closet, collegiate, conjectural, cross-disciplinary,
   devoted to studies, diligent, donnish, dryasdust, erudite,
   extramural, graduate, graduate-professional, hypothetic,
   hypothetical, ideal, idealistic, imaginary, impractical,
   interdisciplinary, interscholastic, intramural, ivory-tower,
   learned, lettered, mandarin, moot, notional, owlish, pedagogic,
   pedagogical, pedantic, postgraduate, postulatory, preceptorial,
   preschool, professional, professorial, professorlike, rabbinic,
   scholarly, scholastic, school, schoolish, schoolmastering,
   schoolmasterish, schoolmasterlike, schoolmasterly, schoolmistressy,
   schoolteacherish, schoolteachery, speculative, studious,
   teacherish, teacherlike, teachery, teachy, theoretical, tutorial,
   university, unpractical, unrealistic, utopian, visionary