The Collaborative International Dictionary of English v.0.48:

Academy \A*cad"e*my\, n.; pl. Academies. [F. acad['e]mie, L.
   academia. Cf. Academe.]
   1. A garden or grove near Athens (so named from the hero
      Academus), where Plato and his followers held their
      philosophical conferences; hence, the school of philosophy
      of which Plato was head.
      [1913 Webster]

   2. An institution for the study of higher learning; a college
      or a university. Popularly, a school, or seminary of
      learning, holding a rank between a college and a common
      school.
      [1913 Webster]

   3. A place of training; a school. "Academies of fanaticism."
      --Hume.
      [1913 Webster]

   4. A society of learned men united for the advancement of the
      arts and sciences, and literature, or some particular art
      or science; as, the French Academy; the American Academy
      of Arts and Sciences; academies of literature and
      philology.
      [1913 Webster]

   5. A school or place of training in which some special art is
      taught; as, the military academy at West Point; a riding
      academy; the Academy of Music.
      [1913 Webster]

   Academy figure (Paint.), a drawing usually half life-size,
      in crayon or pencil, after a nude model.
      [1913 Webster]

WordNet (r) 3.0 (2006):

academy
    n 1: a secondary school (usually private)
    2: an institution for the advancement of art or science or
       literature [syn: academy, honorary society]
    3: a school for special training
    4: a learned establishment for the advancement of knowledge

The Devil's Dictionary (1881-1906):

ACADEMY, n.  [from ACADEME]   A modern school where football is
taught.