The Collaborative International Dictionary of English v.0.48:

Challenge \Chal"lenge\, v. t. [imp. & p. p. Challenged; p. pr.
   & vb. n. Challenging.] [OE. chalengen to accuse, claim, OF.
   chalengier, chalongier, to claim, accuse, dispute, fr. L.
   calumniar to attack with false accusations. See Challenge,
   n., and cf. Calumniate.]
   1. To call to a contest of any kind; to call to answer; to
      defy.
      [1913 Webster]

            I challenge any man to make any pretense to power by
            right of fatherhood.                  --Locke.
      [1913 Webster]

   2. To call, invite, or summon to answer for an offense by
      personal combat.
      [1913 Webster]

            By this I challenge him to single fight. --Shak.
      [1913 Webster]

   3. To claim as due; to demand as a right.
      [1913 Webster]

            Challenge better terms.               --Addison.
      [1913 Webster]

   4. To censure; to blame. [Obs.]
      [1913 Webster]

            He complained of the emperors . . . and challenged
            them for that he had no greater revenues . . . from
            them.                                 --Holland.
      [1913 Webster]

   5. (Mil.) To question or demand the countersign from (one who
      attempts to pass the lines); as, the sentinel challenged
      us, with "Who comes there?"
      [1913 Webster]

   6. To take exception to; question; as, to challenge the
      accuracy of a statement or of a quotation.
      [1913 Webster]

   7. (Law) To object to or take exception to, as to a juror, or
      member of a court.
      [1913 Webster]

   8. To object to the reception of the vote of, as on the
      ground that the person in not qualified as a voter. [U.
      S.]
      [1913 Webster]

   To challenge to the array, favor, polls. See under
      Challenge, n.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

challenged \challenged\ adj.
   1. having doubts expressed about its truth.

   Syn: disputed, questioned.
        [WordNet 1.5]

   2. handicapped or disabled; -- used as a euphemism,
      especially in combinations; as, physically challenged;
      mentally challenged.
      [PJC]