The Collaborative International Dictionary of English v.0.48:

Cadet \Ca*det"\, n. [F. cadet a younger or the youngest son or
   brother, dim. fr. L. caput head; i. e., a smaller head of the
   family, after the first or eldest. See Chief, and cf.
   Cad.]
   [1913 Webster]
   1. The younger of two brothers; a younger brother or son; the
      youngest son.
      [1913 Webster]

            The cadet of an ancient and noble family. --Wood.
      [1913 Webster]

   2. (Mil.)
      (a) A gentleman who carries arms in a regiment, as a
          volunteer, with a view of acquiring military skill and
          obtaining a commission.
      (b) A young man in training for military or naval service;
          esp. a pupil in a military or naval school, as at West
          Point, Annapolis, or Woolwich.
          [1913 Webster]

   Note: All the undergraduates at Annapolis are Naval cadets.
         The distinction between Cadet midshipmen and Cadet
         engineers was abolished by Act of Congress in 1882.
         [1913 Webster]

   3. In New Zealand, a young gentleman learning sheep farming
      at a station; also, any young man attached to a sheep
      station.
      [Webster 1913 Suppl.]

   4. A young man who makes a business of ruining girls to put
      them in brothels. [Slang, U. S.]
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

cadet
    n 1: a military trainee (as at a military academy) [syn:
         cadet, plebe]

The Free On-line Dictionary of Computing (19 January 2023):

CADET

   Computer Aided Design Experimental Translator.

   [Sammet 1969, p. 683].

   (1994-11-29)