The Collaborative International Dictionary of English v.0.48:

Expiate \Ex"pi*ate\, a. [L. expiatus,p. p]
   Terminated. [Obs.] --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Expiate \Ex"pi*ate\, v. t. [imp. & p. p. Expiated; p. pr. &
   vb. n. Expiating.] [L. expiatus, p. p. of expiare to
   expiate; ex out + piare to seek to appease, to purify with
   sacred rites, fr. pius pious. See Pious.]
   1. To extinguish the guilt of by sufferance of penalty or
      some equivalent; to make complete satisfaction for; to
      atone for; to make amends for; to make expiation for; as,
      to expiate a crime, a guilt, or sin.
      [1913 Webster]

            To expiate his treason, hath naught left. --Milton.
      [1913 Webster]

            The Treasurer obliged himself to expiate the injury.
                                                  --Clarendon.
      [1913 Webster]

   2. To purify with sacred rites. [Obs.]
      [1913 Webster]

            Neither let there be found among you any one that
            shall expiate his son or daughter, making them to
            pass through the fire.                --Deut. xviii.
                                                  10 (Douay
                                                  version)
      [1913 Webster]

WordNet (r) 3.0 (2006):

expiate
    v 1: make amends for; "expiate one's sins" [syn: expiate,
         aby, abye, atone]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "expiate":
   amend, atone, atone for, compensate, compensate for, correct,
   cover, do penance, fill up, give and take, give satisfaction,
   indemnify, live down, make amends, make compensation, make good,
   make matters up, make reparation, make right, make up for,
   pay back, pay the forfeit, pay the penalty, propitiate, put right,
   recompense, rectify, redeem, redress, remedy, repair, repay,
   retaliate, satisfy, set right, square it, square things