Source : Webster's Revised Unabridged Dictionary (1913)

Callisthenic \Cal`lis*then"ic\, a., Callisthenics
\Cal`lis*then"ics\, n.
   See {Calisthenic}, {Calisthenics}.

Source : WordNet®

callisthenics
     n : light exercise designed to promote general fitness [syn: {calisthenics},
          {calisthenic exercise}, {callisthenic exercise}]