Source : Webster's Revised Unabridged Dictionary (1913)

Expiatory \Ex"pi*a*to*ry\, a. [L. expiatorius: cf. F.
   expiatoire.]
   Having power, or intended, to make expiation; atoning; as, an
   expiatory sacrifice.

Source : WordNet®

expiatory
     adj : having power to atone for or offered by way of expiation or
           propitiation; "expiatory (or propitiatory) sacrifice"
           [syn: {expiative}, {propitiatory}]