The Collaborative International Dictionary of English v.0.48:

Cycle \Cy"cle\ (s?"k'l), v. i. [imp. & p. p. Cycled. (-k'ld);
   p. pr. & vb. n. Cycling (-kl?ng).]
   1. To pass through a cycle[2] of changes; to recur in cycles.
      --Tennyson. --Darwin.
      [1913 Webster]

   2. To ride a bicycle, tricycle, or other form of cycle.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cycling \Cy"cling\ (s?"kl?ng), n.
   The act, art, or practice, of riding a cycle, esp. a bicycle
   or tricycle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cycling
    n 1: the sport of traveling on a bicycle or motorcycle