NOUN (3)

1. a cavalry unit consisting of two or more troops and headquarters and supporting arms;

2. an air force unit larger than a flight and smaller than a group;

3. a naval unit that is detached from the fleet for a particular task;

The Collaborative International Dictionary of English v.0.48:

Squadron \Squad"ron\ (skw[o^]d"r[u^]n), n. [F. escadron,
   formerly also esquadron, Sp. escuadron, or It. squadrone. See
   Squad.]
   1. Primarily, a square; hence, a square body of troops; a
      body of troops drawn up in a square. [R.]
      [1913 Webster]

            Those half-rounding quards
            Just met, and, closing, stood in squadron joined.
                                                  --Milton.
      [1913 Webster]

   2. (Mil.) A body of cavalry comprising two companies or
      troops, and averaging from one hundred and twenty to two
      hundred men.
      [1913 Webster]

   3. (Naut.) A detachment of vessels employed on any particular
      service or station, under the command of the senior
      officer; as, the North Atlantic Squadron. --Totten.
      [1913 Webster]

   Flying squadron, a squadron of observation or practice,
      that cruises rapidly about from place to place. --Ham.
                                                  Nav. Encyc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

squadron
    n 1: a cavalry unit consisting of two or more troops and
         headquarters and supporting arms
    2: an air force unit larger than a flight and smaller than a
       group
    3: a naval unit that is detached from the fleet for a particular
       task