The Collaborative International Dictionary of English v.0.48:

jock \jock\ n.
   1. a person trained to compete in sports; an athlete.
      [WordNet sense 1]

   Syn: athlete.
        [WordNet 1.5]

   2. A jockstrap.
      [PJC]

   3. A disk jockey.
      [PJC]

   shock jock a radio talk-show host who is notorious for
      voicing unpopular, controversial, or shocking opinions
      guaranteed to offend many people.
      [PJC]