The Collaborative International Dictionary of English v.0.48:

Repay \Re*pay"\ (r?-p?"), v. t. [imp. & p. p. Repaid (-p?d");
   p. pr. & vb. n. Repaying.] [Pref. re- + pay: cf. F.
   repayer.]
   1. To pay back; to refund; as, to repay money borrowed or
      advanced.
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            If you repay me not on such a day,
            In such a place, such sum or sums.    --Shak.
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   2. To make return or requital for; to recompense; -- in a
      good or bad sense; as, to repay kindness; to repay an
      injury.
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            Benefits which can not be repaid . . . are not
            commonly found to increase affection. --Rambler.
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   3. To pay anew, or a second time, as a debt.
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   Syn: To refund; restore; return; recompense; compensate;
        remunerate; satisfy; reimburse; requite.
        [1913 Webster]

WordNet (r) 3.0 (2006):

repay
    v 1: pay back; "Please refund me my money" [syn: refund,
         return, repay, give back]
    2: make repayment for or return something [syn: requite,
       repay]
    3: act or give recompense in recognition of someone's behavior
       or actions [syn: reward, repay, pay back]
    4: answer back [syn: retort, come back, repay, return,
       riposte, rejoin]